My approach to this is pretty simple, they come in pairs, they wear out and it's more a routine maint issue that it should be a "repair" issue (you have a repair issue obviously). They aren't super expensive, and cheap compared to the potential damage if they break(you got lucky).
To do one means I have all the tools out or rented (ball joint press and the 35mm socket. torque wrench aren't really something most non mechanic or Hobby types will have on hand) so if doing one, may as well take the extra hour and do the other.
I anticipated that my Tie Rods may be getting along, I was surprised however how far along they were because my steering was quite tight. When I took the tire/wheel off yesterday to start work on the LBJ's I wasn't "sure", even with parts on hand, I would do the tie rods, and saw that one side the tie rod boot was weather torn I decided to change them out, when I actually grabbed it and moved it I was "wtf!" because it moved far too easily and had play. The Tie Rods inner and outer will add maybe 45 mins to you LBJ job (for someone that has never done before, about 20 for one that has)and can be done easily under $60 or so using good quality parts. Worth it IMHO.
All this leads to the upper ball joints that are on the control arms. Check them while there and replace if needed, that will add another hour, maybe two tops and if you get parts online $100 or so, local auto store about $200.
Having the LBJ's, Upper Control arms/BJ and Tie rods inner and outer done at the shop will cost you $700-1200 to get done. With a 6 hour day available you can get it done and save yourself easily $500-800.
You can even buy the tools and have them on hand for next time around. I got the 35mm socket in a set from harborfreight using a 20% off coupon for $32 (why not get the set when a single 35mm socket is gonan run $20 alone)to do the job (yesterday was my first shot at the jeeps, last time was recall so didn't do and don't need the 35mm socket on my pickup).
https://www.harborfreight.com/12-in-dri ... 62842.html The ball joint press you can rent free at a auto shop, they just take a deposit. I have one I got on ebay a couple years ago that is fine for my very occasional use . here is the set and it's fine
http://www.ebay.com/itm/4-IN-1-BALL-JOI ... Sw3v5Yr9ue)
For this application a harbor Freight torque wrench is fine. $20. $16 if you buy with a 20% coupon (I bring my daughter when I want to buy two things and use the 20% HF coupons, she buys one and I buy the other.. and also normally get a tape measure or something like with their "free with any purchase coupon" for.
Anyhow, so specialty tools for the job you can get for just under $100, or you can rent them for free at the local auto place (I like having the tools on hand, then again I maintain 3 cars and a mower and live in the country so a hour round trip to the auto place to rent something is annoying, plus I am a man and I like owning tools I don't use often..LOL
Anyhow, also do your front brakes when you are in there, you need to take them apart and back together anyhow and unless they are more than half life left, brake pads you can get decent ceramics for less than $30... (I get the rockauto clearance emails so when I see stuff like that that are decent quality I tend to get them in anticipation of using..the ceramic pads I am putting on while I did this job cost me all of $9 and a few inches of shelf space in the garage the last 8-9 months. My rotors are still good so they aren't getting changed.
You WILL have to get the alignment done after you are finished. that will cost you $100 or so. When i buy a new vehicle, first tire change I buy the Lifetime alignment at the local Tires Plus place, then when I do this job i show up and have them align it after.. sometimes I get the eye roll, others they cheerfully do it, either way it gets done and I save myself a grand doing a complete (almost) refresh of the front end. That grand can pay for a family stay at the beach or just keep it off the credit card if the budget is tighter. My thought process on cars is that I generally buy a 2 year old car (jeep i got new on lot after it sat there for 10 months, 22k out the door sticker was 29) with less than 36k on it. Normally save about 40% off new price that way, then I find a brand warranty online to 100k normally for $700 or so versus the 2k the dealer locally sells it for and the first 100K are covered. Keep the vehicle for at least 12 years, the last 6 or so there is no warranty but will tackle most work myself unless it involves something like a transmission rebuilt. I make sure I do all the maint. religiously as that save s a fortune. The money I have saved doing it this way will literally allow me to buy the replacement vehicle for cash..so I never have a car payment. Of course only reason I can do this is I don't care what people think about what I drive, don't feel need to buy new and am willing to do the maint and repairs myself. I must say, it's darn easy now with Youtube and forums like this versus the old pre internet days of a Clymers manual when i was doing repairs because I was broke.
EDIT_ I just saw you were in EU, so Harbor freight tips don't apply, however you can modify most of these tips for use there I am sure, especially with the internet
When you say that replacing the LBJ's could cost me between 700-1200, you mean the 2 in the front or just one?