Ask for the records of the work done in '96. The word "restoration" is used loosely and all too often. Find out if there was extensive (or any) rust repairs done and if so inspect the areas mentioned. Either way lift the carpets, poke around the floors from both inside and under the car. When I say poke I mean poke with a small tool to see if metal is solid. The sunroof seal looks to be painted. No big deal to replace, but approx $500 to have it done right. Check all electrical...for some reason most E9's have suffered from backyard electrical wizards who insist on intalling big stereos and car alarms and in the process mess the rest of the electrical system up. And on and on....water pump, thermostat, fan clutch, control arms, bushings, rubber seals, trim and then the interior!!! All expensive if they need to be addressed.
As for valuation, this car is a great color combination and, if solid and you do not mind the aluminum large bumpers it is worth what you are comfortable with. These cars are not getting any cheaper and have begun to actually appreciate! I think as a whole the cars continue to be way undervalued. Excellent cars are commanding $40+, good drivers can still be had for the mid teens to mid twenties, and projects are low teens and below depending on condition.
Good luck with this one. If it does not pan out for you I would be interested to learn what you found in your inspection. Remember, rust is the abyss. Where there is a little there is usually much more behind it.