An update:
It took me 10 hours to fix the leak (I know, I'm s-l-o-w). I had a bottle jack and some boards.
First I had to lift the drivers side of the bed to get enough room to remove the fill and vent hoses, then raise the bed couple more inches (a total of around 6", wiring for light in bed attached to tannoue (sp?) cover and backup lights limited height of lift). I needed this room to get the supply and return couplings off. Worked for an hour just to get the return to come loose. It was corroded onto the steel line.
I have to lower the tank to get at the lines. I only had about 5 gallons in the tank, so it wasn't too hard to lower. I then had to jack up the frame to easily get the tank out from under the truck.
I degreased the newly exposed frame and while it dried I pulled the module to replace the sending unit (fuel gauge hasn't worked for about 150,000 miles). Fritz's instructions were very good. The 3 screws had loosened and allowed the prefilter to slide down about 1/2". As Fritz suggested, I put a washer under each screw and secured them in the proper location. I also removed the prefilter and cleaned it. It had only a couple specs of dirt - not bad.
I then checked for the leak. There was a pinhole sized leak in the about 8" long plastic return line tubing between the coupling and steel tubing. The tubing had rubbed on the plastic guard Dodge put on the frame to protect these lines! I checked the supply line and there was just a little abrasion on it so I wraped it with electrical tape. I replaced the return line with a length of hose with worm clamps and wraped it with electrical tape for abrasion protection. Hope this works.
I sprayed the inside of the frame and the steel fuel lines with some rubberized undercoat hoping to keep the lines from rusting in the future.
Attaching the two straps that support the tank took a while, they were hard to get back onto their mounting studs - took a lot of prying. Then lower the bed in steps, etc. Reverse of the above.
Fueled up today and ran her 10 - 15 miles. Good news and bad:
Good news: no sign of leaks.
Bad news: full tank and the gauge still reads empty and that light is still on!
Any ideas on the fuel gauge?
Sorry its so long, hope it helps someone else.
Gene