I have replace a couple of windshields.  Unless you can find one in a junkyard
(good luck), the glass will cost you about $350-$400 installed. You can
probably buy just the glass for $200-$250 new and install it yourself.

Yes, it is something you can do yourself BUT if you break it -- no refund!.
It is better to use a new rubber seal (VW price= $99.00 but you can get it
cheaper from West Coast Metric).  However you can save the old one by breaking
the old windshield and taking it out by pieces.  At some point you can then
peel the old seal out undamaged.  Clean it real good with soap and water.
Harsh solvents will deteriorate it.

The replacement takes two people.  First get some heavy duty black butyl
rubber cement.  Your local auto glass shop will sell it to you (mine cost
$10.00 a tube).  Fill the groove of the rubber seal with this cement and put
it on the windshield.  Now fill the groove of the seal that will go around the
metal body window frame with the cement.  Next take some wrapping twine (cord)
and lay it in the groove you just filled.  Pull it tight so it goes down in
the black cement.  Tie it at the top middle of the window seal and let the two
ends hang down.  With your friend outside, lay the windshield into the groove
very gently.  Have you friend push from the outside (gently) until it is
evenly placed all around.  Now while your friend pushes from outside begin to
pull the string inside toward you.  Have your friend follow your movements by
pushing down as the string comes out.  Do this until the string is all the way
out at the bottom middle of the windshield.  The glass assembly will slip
right into place.  Clean up excess cement from your dash (don't use harsh
solvents or your dash will turn light colored).

Good luck.

Russell G.
'85 GL
'93 EV