I just went through all of this on my Dart. Pulled the original tank to clean it out and put in a new sending unit. Took it to a radiator shop to boil it out and seal the insides. That was $100.

After I got it back, I worked for 3 weeks off and on trying to get the new sending unit to seal correctly. Always wanted to seep gas no matter how clean or tight the seal was.

After all was said and done, I ended up buying all new pieces from Quanta Products www.gastanks.com and ended up spending over $400 for everything. It's all new from the pad, to the sending unit, so that part of my car is good for a while.

Could have saved about $100 by buying everything from RockAuto.com They sell the same products at cheaper prices.