I'd say thats all pretty normal.
Saftey features have been built in so that if you were to accidentaly shift into reverse while
driving forward (and vice versa) you dont lock up the transmission and possibly destroy it.
Also, when coasting in N and slamming it back into D, remember that 3rd gear is the default
gear for D. Normal speed range for 3rd is 20-35 mph. If you are coasting at say 45 mph and
slam it back into D, it will make a noticable and loud clunk.
Other times that clunk is just from taking up slack in the driveline.
Try lightly pressing on the the brake when putting it back into D. That will lessen the clunk a
bit.
Or, of course, you could just drive and shift it like a normal person.