Replacing the window regulator isn't that bad. I've done both of mine.
Check out this site...
http://www.bombaydigital.com/boxster/projects/window/
Some notes:
Before you loosen the bottom clamps that hold the glass, use a sharpie mark the edges of the clamps so you can put the glass back on at the same location. Same for the mounting positions at the bottom regulator mounting points inside the door. These determine the angle that the window raises- too far in and the window will hit the top outside of the top weather stripping.
And be careful not to tear the thin gray foam moisture barrier- it's pretty expensive.