Hi Kurt,
I just got my wing back from the paint shop last week and put it on my car. Here is what I learned from all of this.
I grossly under estimated the time it would take me to sand my wing ! My time is cheaper than bodyshop rates for that kind of stuff, but it was still tedious.
I spent a complete weekend doing it because you have to get all of the gelcoat roughed up (I used 600) and if you get any pinholes YOU MUST FILL THEM ! If you don't get them filled, you are wasting your time and money because when you get it painted the paint can't fill those holes.
Make sure you are using the same primer that you painter will use. If you use something that is not compatible they will have to sand it off (read $$$$).
I did all of the sanding, the paint shop shot the 2 part primer then they gave it back and said fill all of the little holes that the primer couldn't fill - and there were LOTS of them. I did that then they did the color coat.
I paid $300 for mine to be painted with me doing the prep. I got some estimates that were $500 to 800. My wing might be a lot bigger than your too, but a lot of them had a minimum.
In the end I think it was well worth it. Here are some pix of it.
Tom Sharpes
90 C2 Targa