If at all possible insist that the shop who does the work use a factory gasket/seal. The aftermarket seals are not as good. How do I know? I've had had several windows replaced over the years using a good glass man, an Independant that has his own truck and is very experienced with installing old window seals. I once provided him with a seal that he said he didn't like because it was from the cheaper source they use at autoglass shops. I think WorldPac
http://www.worldpac.com/ also sells the cheaper seals.
I recommend you pay $10 or $15 more and get a gasket that seals better. If you don't want to pay the extra bucks you most likely will have drips (then rust) or a funny looking corner on the seal for the rest of the life of that windowseal.