Either way the engine is likely going to have to come out. Only when you get it apart will you know if cheaper to Fix or replace. Most times low pressure is due to a rod or crank bearing failure ( rare that oil pump goes out but sometimes does happen). If me, I'd check to see if oil pump bypass is not stuck ( or spring is broken ) causing the problem before pulling. If I remember correctly the relief can be checked on the outside of the engine on LS engine family...
If OK, pulling pan to
Inspect lower end will quickly tell if you have a rod or main issue without having to fully disassemble the entire motor.