95 Jetta With idle and oil light problem

Hey I have a 95 Jetta III GL 2.0 Liter engine with a manual 5 speed transmission. it has 150,000 miles on it. I recently replaced the crank case breather tube assembly as well as the grommet between the oil filter assembly and coolant assembly. I have also replaced the crank case vent valve which is part of the intake system. My problem is my idle jumps up and down when in nuetral and the car seems to be holding back. Sometimes it will idle right at 700 RPM just like its supposed so other times it will fluctuate and/or stall out. Also when I am in gear it gives me and oil pressure warning with the insanely annoying warning buzzer. I am oing to replace the idle stabalizer unit. Do I also need to replace the valve and rod bearings? if so how hard is it to do? I would like to do it myself if possible I am pretty car savy. If there are any questions let me know and i can answer them. Thanks in advance.

For the idle stabilizer problem: Remove it and clean it thoroughly with carb cleaner. That should fix it. The valve itself rarely goes bad.

Oil pressure problem: The problem is frequently one or both of the sensors. Get an oil pressure gage. Harbor freight has them for $10 and use the 1/4 npt fitting. Remove the sensor from the cylinder head and read the expected pressure off the underside of the sensor. Install the gage instead of the sensor and start the car. Let it idle at least 20 minutes and check out the pressure. If it's above the spec, then replace the sensor. Jetta's are built really well and seldom will have significant bearing wear unless they are run without oil. Replacing the bearings is doable, but you'll want to pull the engine and trans first. You don't have to, but I wouldn't change the bearings without taking the block and crank to a machine shop and having them checked out.

Ok sounds good and easy enough to do. The car was driven home from somewhere by the previous owners with the grommet between the oil filter and cooling systems being bad. It lost a lot of oil on that trip home. Sometimes there is a bearing tap but it does go away. I am assumming this would mean bearings need replacement. How much would it run me in a shop to have this work done? Also the engine itself sounds clean. No sputter when revving or driving. Sounds smooth in high RPM. No audible rattle just the occasional bearing tap. I will do the rest of the sensor stuff myself thanks again!

The hydrolic lifters need to get "pumped up" and tend to make a bit of cam noise for the first few minutes until the oil is heated up.