You shouldn't have to tear everything apart to get at the pump; just pull the right front tire off, lay back the wheelwell rubber mud shield and access the pump thru the wheelwell, from underneath the intake manifold.

Note that there will probably be a bit of residual oil coming out when you pull the pump, that's just whatever seeps past the fuel pump pushrod. There'll be less if you let the rig sit and drain any oil from the top end before you remove the pump.

You can look up the part # for your pump at http://www.isuzuparts.com/part_number.html

Re: what pump to get, be sure the one you select is a mechanical fuel pump for carbureted model. You will probably find other listings for electric in-tank fuel pumps, those are for EFI models.

Cheers and Happy Turkey Day............ed