[Too Cold NB1.8T]

Since your car problems began after the new engine was put in, it is very possible that some wiring or something was damaged during the install which could be the cause of your present battery drain issues.

On the New Beetle, removing/installing the 1.8t engine is no simple task, for anyone who plans to have this done, I would suggest biting the bullet expense wise and letting the VW Dealer do the job, too many things can be screwed up by letting someone do this who is not intimately familiar with this car.

Hopefully the problem is a minor one like with the radio as you mentioned, in the future I'd suggest sticking with a VW dealership for any services or repairs that you don't do yourself and for outside work like an upgraded audio system etc., find a highly regarded but qualified specialist, talk to the owner or manager and make sure that their work is completely guaranteed in case any problems appear.

You may want to find a different dealership than the one that says everthing is a blown fuse, either that or have a heart to heart chat with the service manager, GM or dealership owner if you are not being treated properly, if your not working on your own car and if you don't have a worthy friend/mechanic you can trust then dealership is your best bet, bar none.