1) Do a search for something like
www.clarks-garage.com . Its a 944 board. LOTS of FAQ's and guides about 944 buying. Also model year breakdowns and changes.
Pre 1985.5 will have the "old dash" which is well, old. Post 85.5 will have a more modern dash with useable dash vents.
No N/A 8V 944 is "fast". 150hp. not easy to "make faster". If speed is your need, look for a Turbo now. Don't even think you can make an NA fast, unless you drop in a chevy V-8.
Its a 20+ year old car. Likely had a few owners.
Timing Belts/Water Pumps are the key maintenance items. Clutches too (as a replacement is quoted at about a bazilliion shop hours - figure $2k) so, figure that a new clutch, belts and wp could be as much or more than the cost of the car! Then you realize why many people simply "abandon" 944's when they break.
Steering racks are big $$ too so check that out thoroughly.
No mention of mileage on the car in the ad. Or about maintenance history. 944's can be cheap to buy, but NO porsche is cheap to properly maintain.
Also realize, its a 20 + year old car. Some parts may be getting harder and harder to find.