Just found out my misfiring code is because of a bad exhaust valve in cylinder 4. I'm a ranger newbie (just bought the truck off Craigslist 2 weeks ago). I'm a DIY kind of guy but don't like to wade into auto repair jobs that can't be done with a simple wrench set and Haynes Manual. Can I fix this myself? What would I need to replace to get this running smoothly again? Should I just buy a used engine and switch it out? Any advice would be greatly appreciated!