I installed a Robbins glass window top a couple weeks ago. It's not super difficult, but if I did it again, I would do things in a slightly different sequence.
It's a $700 top brand new, and if it's still in it's shipping box, it's still worth most of that price. $400 would be a low-ball offer, IMHO.
I'm taking the top to a shop to have it adjusted, because IMHO, I just don't want to have to go back and correct a couple things. If I were to give you advice, and you followed it, you shouldn't have any issues. Learn from my experience!
Let me know if you have any questions. I still need to write up a little review of the process and send it to Mike Focke. There are a few tips I think would really help people when installing their own tops.
Honestly, it's really not that difficult. With hindsight being 20/20, if I could go back in time and do it over, it would have turned out fine.
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2001 Boxster - Grey on Grey
1969 911T Targa - 'Stinky'
http://www.zoto.com/frayadjacent/img...f27a-4a399.jpg <---- my car. ^ crap I post.
"The existence of the flamethrower is evidence that someone, somewhere once said 'I want to set those people over there on fire, but I don't want to have to walk over there to do it.'"