Depending on the mileage, you may have a problem that does not require an engine replacement. A valve seal problem can cause an excessive amount of oil burning as well as a few other things.
The shop should do a complete inspection of the engine rather than just say you need a new engine and ask you for a blank check.
You may only need to remove the heads and have then rebuilt. You may also have some failed gaskets and seals that need replaced. All of those are a lot cheaper, and more probable, than a worn out engine.