Assuming you're driving an 88, your car is about 27 years old. As any fabric ages, it becomes weaker (UV damage anyone?). I would strongly discourage dying the belts, however, it's your car.
When I had mine redone, the local shop charged $95 per side. I heard that at one time there was a group deal for another shop that was around $65 per side. The Fiero Store sells rewebed and mechanically rebuilt seat belts for about $220 if I recall correctly. When you take your belts off, ideally you'll want to use a T47 bit, however, you may have luck with a T50 bit if it's all you have.
'85 V6 SE 4sp (SOLD)
'88 GT - Series 3 SC3800 w/ 3.5" pulley, 1.8" rockers, 3" exhaust, 3.5" intake, 3.29 gearing. Installed and tuned by Sinister Performance
'99 Kawasaki Vulcan 500, owned since new
'09 G37x Sedan w/ Premium & Nav (wife's car)
'13 G37xS Sedan (new daily driver)
'14 Yamaha FJR - 0-60 in 2.8s w/ 34MPG!!!
[This message has been edited by Chris_narf (edited 05-09-2015).]