Must be similar to the 2nd gen. 3.2/3.5 in those areas.
Probably better than RTV for providing a good seal with new water pump rear o-rings would be J-B Weld to fill the corrosion pits and then filed/sanded down flush. That's what some here have done on the same problem on 2nd gens. RTV might work, but I personally would trust a J-B Weld-as-filler repair more for that.
On the rear cam plates, again, I don't know if they are the same design as the 2nd gen. in that area or not, but if so, I know that the 2nd gens take a standard -136 size o-ring, so if you could find that locally, that would do it. If you had time (and, again, if it's the same design as the 2nd gen. in that area), I'd recommend buying a bag-o'-10 Viton -136 o-rings off of ebay (for less than $10), Viton being a better material than regular buna-N/nitrile. Again, RTV might work - it's oil, but not under pressure. On the 2nd gen., one of the cover plate bolts goes into a thru-hole, so you'd need to put RTV or other type of sealer on the threads of that one bolt in addition to whatever you seal the cover plates with.
Sorry if anything above doesn't apply to 1st gen. If not, then hopefully someone can provide the 1st-gen.-specific info.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs