You can definately do it yourself. But it is a tricky process to explain without pictures. I think if you do a search on "hardtop installation" you might find some helpful tricks.
When I bought my hardtop, I had the dealership fax me the instructions. They're kinda useful.
Here's a post I found helpful.
http://986forum.com/forums/showthread.php?t=1607&highlight=hardtop+installation