96 7.3 oil pressure gone wild

[Mudwieser]

I have a 96 250 PSD. I just replace my batteries and now its getting harder to start, and once started I noticed that my oil pressure is low and then will suddenly jump up to normal. It has never done this before, changing my batteries is probably just a coincidince. Can anybody tell me where to check my HPOP pressure to tell if it is getting weak, its got 200k + miles so changing it would be a good thing but I havent had any power loss or major problems till now.

Thanks guys, Joe