This past summer I replaced the lower valve cover gaskets on my 993. It was quite the job with the turbos in the way.
I was going to replace the uppers but with the 96 TT's power steering pump is in the way, so I didn't replace them. Talked with some folks and they said they hardly ever change the uppers because of the difficulty and they don't leak very often anyway.
I've got the upper gaskets for the 3.6L that I wont be using so, if anybody can use them, they're $20 and free shipping.