OK, it's tired.
How do you know it's overheating? What is the temp gauge showing? What temp does the computer think the engine is at when you connect a scan tool and look at the temp sensor data?
If this is a head gasket that leaks and pressurizes the cooling system, it may not be overheating at all.
Depends on your skill level, experience, the tools you have or have available, the availability of a decent machine shop local to you, and whether you have a secure and CLEAN place to do the removal, teardown, inspection, cleaning, assembly, and reinstallation. Are you prepared for all that?
Buying a "new" or "rebuilt" engine will be easier and probably quicker; but also more expensive. You're trusting someone else to do a big job correctly.
In addition to the actual engine, you're probably going to need a fresh radiator, fan clutch, fluids and filters, exhaust work, and various accessories--water pump, distributor, belts 'n' hoses, and more depending on what you find as you disassemble.