If a proper head gasket repair is unfeasible and the leak is small, a chemical head gasket repair may put a bandaid on it for a bit. Some rave about Blue Devil, and I’ve heard good things about K&W Block Sealer. Either one or some others may seal the leak and give you some additional time. I’d try that before doing nothing. Leaks like this have a nasty habit of becoming a big thing really quick and at the worst times.
Sometimes, if you have lived a good life, given to charity, and are really lucky, re-torqueing the head bolts can stop a small head gasket leak. It might be worth a try anyway. I’ve never done it myself. There may be some precautions. Like you don’t want to snap off a bolt head in the process. Maybe the experts here can offer some guidance if you decide to try it. I’d be inclined to first loosen all he bolts a half turn, then re-torque them.
GeorgeSanJose: Yes, I asked the garage specifically if they would just replace the head gasket. I think concerns for other potential problems and potential customer dissatisfaction (as you stated) are reasons that they would not do the work. They specifically recommend used motors which they will warranty for 6 months.
oldtimer 11: The radiator fans work fine. The van is loosing coolant with no apparent leaks (pressure tested three times). It does seem to be a blown/damaged head gasket.
insightful: I heard about $1500 for a head gasket job, so roughly in the same ballpark. I had hoped (assumed) that a leak-down test could identify which cyclinder(s) was (were) affected. I assumed that only one head would be affected. My next step is to see if I can find a garage that would do a leak-down test and only replace the bad head gasket–though I am not certain how much more money I want to put into this vehicle.
BustedKnuckles: I will look into the chemical head gasket repair depending on how things go with finding a garage which is willing to replace only the bad gasket (along with any machine shop work).
All: Thanks for your comments and suggestions.