That's a high price, but not sure if the Venture requires anything funky to get at that rear cylinder head. IIRC the Safari vans/Astro Vans GMC used to make required you to remove the front suspension to drop the engine far enough to do that repair. Stupid design.
I would say a head gasket repair on average should cost around $700-1000.
Then again, I once took a junked Mazda 626 from a girl for $125. Head gasket went up. Price to fix it? $1100. Cost of head gasket? $900. No kidding. Dealer-only part, and the gasket was almost $900. Not worth the price of admission in that case.
