The OP is talking about taking his car to a Porsche dealer, so one can assume that they have experience with Porsches.
That said, I'd take it to an alignment shop that specializes in sports cars and specialty cars. Usually in any good-sized city there are places like that. The reason I recommend a place like that is because they'll do a better job than a dealer or most tire stores, because they'll take the time to make sure everything is set to the proper specs, not just adjusting it to get into the "green" area.
There is nothing special about getting an alignment on a 986, they are pretty straightforward. You just want the alignment tech to get all the values right, and consistent side-to-side.
$130 does seem like a pretty decent price. When I got my alignment done after rebuilding the suspension, it cost me $125 (in Seattle) at a place called Truline. The tech set it exactly to my specs. The car he had done just before mine was a 911 Turbo, BTW.
