To date I am not aware of a KK engine swap how-to. We are getting to the point though where some of the '08's are getting up there in mileage and it is probably a matter of time before somebody will want or need to attempt it.
My original 3.7 threw a rod bearing at 86,000 miles. It was a totally freak thing, as I always changed the oil every 3-4,000 miles and kept up with maintenance. I ended up going with a Jasper remanufactured engine professionally installed by a local mechanic. My Jeep was in fine shape otherwise and had a good number of modifications already, so I was in no hurry to go Jeep shopping. The cost of a new engine was less than 20% the cost of a new KK at the time. There is something to be said for no new car payment, and I really like my KK! The Jasper engine came with a 3 year, 100,000 mile warranty, too.
I know not everyone in that situation will be able to afford a remanufactured engine, but low mileage junkyard 3.7's are readily available. Here is the most informative thread I know of for swapping a 3.7 into a Liberty. It's a KJ and it's an '05 engine into an '03, but this thread will give you an idea of what to expect if attempting an engine swap yourself on a Liberty. Thanks to TwoBobsKJ for a fantastic write up over on JeepKJ!
http://www.jeepkj.com/forum/f202/engine-swap-overview-53270/