Should I replace my engine

Get a second opinion. Some salvage yards will install their used engines. $4200.00 seems awfully high. It might be less expensive to have your engine rebuilt. Another thought, if you can wait a few weeks, is to look for a community college with an Automotive program. We were always looking for live work to give the kids real-world experience. They are well-supervised and conscientious. You'll pay for parts and a little labor but the trade-off is you'll have to wait until what you need fits what they're currently teaching.