I've got the exact same problem. Had trouble getting it to crank over, turned out to be a fried ECU Relay, but when I dropped the tank to look at the fuel pump, I spent 20 minutes just chiseling out the dried mud and dirt clumps to get to the bolts. I am afraid of what I'll find if I get a power sprayer up under that bad boy. I see rust all over and I know that in the mountain areas they salt the roads which is obviously rust fuel. As to the extent of the damage, hard to say, just thought that while I'm building it up I'd ask the experts.

3.2L V6 SOHC 1996 Isuzu Rodeo. Flowmaster exhaust / K&N High Flow Intake / Kenwood headunit / Audiobahn Subs / Alphasonik/Kenwood/Sony Amps / 180 amp High-output alternator / Redtop Optima battery / Custom hood w/ scoop