Oil pressure problem..

I know there are several threads about oil pressure but none that answered my q's, so here goes.
90 xj 4.0 auto w/ full gauge package, I have owned this Jeep for better than 3 years. When I bought it the oil pressure gauge didn't work at all, it was just pegged out all the time but ran fine. After about a month I bought a new sending unit that worked but still had my pressure screwed up, so here is what I have now.
When I start the jeep and let it idle the oil pressure (op) goes up to just over the first line and stays there until the motor warms up. After the motor warms up it drops to Zero, but still runs fine. The reason I am suddenly worried about this is because Saturday morning I started the Jeep and the bearing gave me that 2 second rattle then ran fine. It also does this just about every time I start the Jeep.
This weekend I plan on changing, oil pump, main and rod bearings (from the bottom) rear main seal, oil pan gasket and the oil filter adapter because it to is leaking oil pretty bad. I just am wondering if there is anything else I should do while I am there and also does it sound like I am even going in the right direction?

Thanx Abunch Digger

Before you change the mains, do a check with plasti gauge. The mains can be tempermental, if they are within specs or within allowable outside specs. I wouldn´t mess with them. They rarley wear perfectly flat and a new set of bearings, will often only contact on one edge, which can cause heat failure. If you plasti gage the connecting rod bearings, check the top bearings, that's usually the one that wears the most.
You don't really have to check all the mains, just a sample, the rear seems to be a trouble spot.
Spray out the cap bolt holes and use Loc Tite. Whatever you do, mark the caps, left end or right end and number. They are often stamped, but why trust somebody else. I use a pointed punch and put dots in one end, the wifes 87 had two number 5, connecting rod bearing caps in it.
I could be confusing the XJ with the YJ, but a poor power connection will make the gauge read low and a poor ground will make them read high. Before I change much, I pull the sender and hook up a mechanical pressure gauge there and see what I really have.
Before you test with plasti gauge, all the oil has to be cleaned off, plasti gauge is oil soluable, it will melt in oil, but you can leave it in, for reassembly.