I did these awhile ago for my '87NA 944 - with vinyl skins from Only944 (sourced from a manufacturer in Calif. using "Porsche Spec" vinyl)...costing under 400.00 for the pair. The process did entail lots of very tedious/careful work - which could not be rushed. Took me about 36 hours total I'd guess. At any rate...here is a "before" image, with the new skins in the foreground:
And after I'd finished...prior to using a hair dryer for a bit of touch up on a few minor wrinkles:
At any rate...the seats are holding up well.