Hmm strange.... I responded to this thread yesterday, but the response is gone....
Anyway, here goes again...
I am visiting U-995 this coming Easter as well
as part of a little holiday to visit the parents-in-law.
Hamburg is the closest airport as far as I know.
Trains are pretty good, so if you didn't want to get a car that should be no problem.
Depending on your schedule and time, I can also highly recommend visiting the
Wilhelm Bauer (originally designated U-2540) which is a Type XXI U-boat. This is in Bremerhaven which is not too far away from Kiel.
Well worth the visit.
Enjoy your trip!