Hello. I also have a '97 Guards 986. I scraped the rear passenger side wheel arch and bumper area late year (note it's a UK RHD car). I too was worried about paint match and ending up with a colour contrast and / or an obviously over-shiny area. I had the whole rear passenger wing / fender and rear bumper attended to. The results were way, way better than I expected. The colour match was pretty much perfect. The glossiness matched the rest of the car. The only flaw was on very close inspection in the form of some very tiny flecks of dirt in the paint.
The arch / wing / fender and bumper in question can be seen in the image below taken after the work was done but good enough to make it onto a magazine cover:
I'm afraid I haven't taken any proper images myself since the work was done and I don't have the pictures taken for the mag, but this iPhone snap hints at the colour match - ie it's very, very good.
This work was done by a pretty unassuming local paint shop. Nothing high falutin'. Before the work he said he intended to keep the blowing in / colour painting to a minimum, but he intend lacquer the entire wing / fender. Whether he did this or not, I don't know - the work looked good, I didn't ask whether he stuck to the plan.
Now, the big question is whether the paint was lacquered from the factory. I tried some polish compound on a few panels and found it went pink, suggesting the paint is not lacquered. I think the paint probably did lacquer their work.
Moral of the story - it can be done. Hope this helps a little.