I will second the recommendation for MichiGun. I used them for a transfer sale a few months back--about $30 as I recall, very friendly group. A lot of other dealers got pissy or wanted much higher fees for doing a transfer sale because they felt they were being "cut out" of some part of the deal. One other thing, MichiGun made me buy a stupid $5 cable lock when I picked up the gun; might want to see if you can provide your own and get around that.
There's also a guy who works out of his house under the name LSA Enterprises who only charges $15 for a transfer sale, but he's in Northville and is sometimes hard to get ahold of. If you need more info I'll dig out his phone #...