hi mate, welcome. I can't recall ever seeing Phantom 2 kits with just the gimbal pre-installed... to be honest with you it's really not that hard to install the gimbal, just a few screws and plugging in a cable, the worst part is getting the technique for mounting the rubber dampers but you'll get it pretty quick.
Now I DO know about a multitude of places that sell Phantom 2's with a full FPV kit already installed, including the gimbal. With just the P2+gimbal alone (adding your own gopro) you don't have any way to see what the gopro sees you just have to guess. Most folks go ahead and add in a FPV system so you can indeed see live through the eye of the gopro and know exactly what you're pointed at, and while you're doing THAT you also want an iOSD for telemetry info. Head on over to the FPV forum if you want to learn about all that
It's really not hard to install one of those systems yourself (total cost under $400) but I totally understand if you don't want to deal with it and just have someone else do it all for you. I actually have started doing this for folks but only in the NYC area, so if you happen to be nearby we can talk but I don't want to deal with shipping and all that.
B&H sells fully built P2+FPV kits as do a plethora of other vendors, not sure if any of them specifically have a H4-3d. You could also look in the Classifieds section of this site, I know a guy with the handle "hunch" that buys, repairs and sells Phantoms with full kits, carrying cases, etc. if you go track down one of his threads in Classifieds he might be willing to set one up with a H4-3D for you. Bear in mind you can't PM people on this site until you hit a 5 or 10 post count (you're currently at 1) so if you want to PM him go make some comments on some random threads (the Photo/Video forum is useful for this.. just say "cool!" or whatever on a few posts)
Someone also just posted
this H4-3D with FPV kit in Classifieds (ebay link) although you could build the same kit yourself for about 300 less, it's not a bad deal if you consider the $300 build time and all.