I had the exact same problem. Used some "radiator stop-leak-mess" and its been holding up for 6 months now.

I'm sure there will be a big stink from others on the forum about using or even suggesting that, but in some cases I'd consider doing it myself. Like say the engine is on is last leg and about ready for the scrap pile anyway. In that case I'd close off the heater core to prevent it from getting clogged up until all that stuff was flushed out. Or say the whole vehicle isn't worth the cost of repairing it. I've got an old Taurus that I bought to have something to drive while I did my 3.4 swap, its probably worth less than what someone would charge to replace the HG. If it came down to towing it to a bone yard or the stop leak stuff, why not give it a try?

I thought about doing it.. but I love my truck and I want to do it right. Plus.. I don't want anything else going wrong soon after.

My mechanic will do the HG, timing belt, valve covers, fix my power steering leak, machine heads for $1500. I should have the truck back in about a week.

Good luck with it, sounds like he's doing a good job for ya.