I thought perhaps I could help save someone some time or aggravation if you choose to drop the fuel tank and swap the pump and or sender, etc. I did it this weekend so I will share some of my thoughts... The vehicle is a 4WD Jimmy SLT 1995.
When dropping the tank, use a car jack and jack it up one 1/4 pump past where it makes full contact with the tank the tank will flex a litltle (this seemed to make it easier to remove the tank straps/bolts)
Check the vent valves on the top of the tank. If they have any signs of cracking, replace them. I bought one at the stealership for maybe $30. I used RTV sealant on the tank before securing the vent it seemed to help it in terms of making it rock solid (these valves turn 1/2 way to ?lock¹ in make sure you set it the right way before you turn it (dry fit it first before using the silicone).
A word about the straps... In both removal and reinstallation, do the front strap first. This is very important when you reinstall otherwise if the bracket comes out of the retainer and the rear strap is tight, you will NEVER get the front strap back on without removing the rear strap/bolt.
The filler hose connection should be made before the tank straps get tightened otherwise it¹s too tight and a PITA. The EVAP line must be connected before the tank is raised or it will be near impossible due to the metal lines and their inflexibility.
I cleaned my tank out with warm water and dishsoap and then methyl hydrate. I let it sit overnight to dry. I washed the exterior of the tank with aluminum siding cleaner and then followed with an aluminum polish and carnubua wax (it seems excessive but I figured it might stave off the rusties for awhile. Don¹t bother reusing that damn lock ring for the pump replacements can be had for a few bucks and i¹t¹s much easier when reassembling.
If you think you need a new pump, be sure to check that damn pulsator. Both sides of that useless thing have almost an internal orange lining/washer that rips eventually and bleeds pressure into the tank rather than the line. If you think the pump is still ok, replace that pulsator with a rubber hose (3² piece and hose clamps). I may have been able to get away with just fixing the pulsator but I decided to put in a new pump (I found one with a lifetime warranty if you want the name ask and I¹ll dig it up).
My fuel sender was ?whonky¹ before I serviced it (false empty and inaccurate under 1/2 tank) and now it works like a charm. I cleaned the variable resistor pack with alcohol and then filled all electrical molex connectors with dielectric grease. I¹m sure this one is obvious but if you have the spare tire mounted underneath, do yourself a favour a pull it before doing work on the tank (you will have enough room to kneel and address the tank fittings facing forwards with both hands rather than contorting too much. If you have a lift then you don¹t have the same issues as I do.
I also replaced the fuel pressure regulator under the plenum with the Help! kit. Make sure you use antiseize on all the fuel fittings and tank strap bolts. A word about mystery leaks in the fuel system. Put a little soap and water over the shraeder valve at the test port. I found I had a very slow leak there that I was able to find with the soap/water. I then uncrewed the valve, cleaned it off with alcohol put a little oil on it and screwed it back in. No more leaks. This leak wasn¹t detectible with a pressure gauge till many hours later.
Sorry if this was a waste of anyone¹s time but I thought even if it helps one person, it might be worthwhile. if everything goes smoothly, you can pull the tank and replace the assy in a day or a few hours if you rush. As for the plenum, once you do it a few times, you can pull it in maybe 20min to an hour tops.
Thanks! Andrew.