So how do I find out if my oil pressure sending unit is bad or if I have a much larger problem? I don’t want to take it to a shop because you know they’ll say it’s not a cheap fix of putting in another sending unit.
You need to check the oil pressure with a mechanical gauge. If you have access to one, do it yourself, but otherwise take it to a shop and say “Please check my oil pressure with a mechanical gauge” and if they won’t, go somewhere else.