Engine oil pressure in my 2014 Mazda CX-5 diesel is low

A second-hand engine from a wreck is often a good an option, but only if you can find one that has been tested and comes with a warranty, otherwise you could be replacing your worn engine with an even more worn one. But with a diagnosis estimate of $5000 (and any actual repairs on top of that) I reckon a different workshop would be your best option. Frankly that seems (on the surface) a ridiculous figure and suggests that the workshop in question either doesn’t want your business or is assuming you’re a sucker.

Low oil pressure can be caused by various problems, and a good workshop should be able to check it out and give you a definitive answer on whether it could be fixed or the whole engine replaced. The good news is that the CX-5 is a popular model, so a replacement engine shouldn’t be too hard to track down.