1988 ford van E-150

how hard is it to drop one or both gas tanks on a 1988 E-150 Ford van. it has been sitting for almost two years with a small amt of gas in each tank 3 to 6 gals each maybe. i have been told to drain and clean tanks and test pumps , i didn’t think this could be done off the vehicle. the hi- pressure pump seems to work , although it is questionable as it has pumped bad gas and a mechanic says it shows a low psi reading, and he believes the in tank pumps might be ok. Once this is done maybe it might start, but last time it ran rough and backfired. I can’t justify spending much money on a vehicle of limited value that my wife wants to get rid of anyway