The old engine might need to be a core as they got a reman engine. the shop needs to keep it.

you made a pretty big oopsie. gonna tell you straight up this is nothing you can do yourself.

brake

shooting the parts cannon at a car isn’t exactly cheaper than having someone diag the issue and solve it once and for all. 10psi is way too low, you should be seeing around 40. what kind of pump did you get? i understand parts might be hard to find for that car but there are still better pumps than others. how are your grounds at the pump?

yeah shops can refuse work. not obligated to work on everything

sure why not