Mechanic wants $2000 for replacement -- do repair kits work? Anyone have experiences good or bad with them?
Long story short, yes it is an option. Whether or not it's a good one is another discussion.
Good News: finding a replacement gas tank and having a competent mechanic replace it shouldn't cost anywhere near $2000. Especially if you find the gas tank yourself. I'd be curious to know how your mechanic intends to fix your gas tank and add up his services to a total of $2000.
Bad news: in-place gas tank repairs are very hit or miss. You can find putty-like products that claim complete and permanent repair of gas tank holes, but these don't always work as advertised. I've known people that have tried all sorts of "tricks" to try and patch a damaged gas tank, the putty products and jb-weld type products included. Some have even tried simply welding the gas tank (this is a terrible idea if you haven't emptied the tank and you're not very careful or very good at welding, hello explosion)
To sum things up, I never mess around with gas tank problems. It makes me feel better to know that I have completely resolved the problem by just replacing the tank. It's too risky to assume that a quick-fix will hold through thick and thin and be able to perform whenever you need it to. Just my 2 cents.
If you've had an accident of some kind there could be damage anywhere on the tank, and that damage might not be apparent. There could be cracks or distortion which weaken it and later cause a catastrophic failure. So to be sure you have a complete repair you would need to get it out of the car so all the damage could be found in the first place. Also, you'd want a welded fix not putties or patches as nothing else is really reliable, and again you'd want the tank out so it could be thoroughly emptied and aired out - fuel fumes in the right concentration are an explosive. If the tank is out of the car you may as well replace it with a new or used tank in good condition as most of the cost is labor.
2000 USD for a gas tank replacement sounds like a total gouge to me unless you have something very unusual, get a second or third opinion.
I used the 2-part putty stick to repair the leaking tank on my 1968 Firebird, while it was actively leaking. I backed into a parking stop and bumped the tank, when it shifted a bit it caused pinholes where the support strap was contacting the tank. I was young and broke, so I never had a chance to replace the tank. The putty repair lasted 1 1/2 years until I completely wrecked the car and sent it to the junker.