I have a 1994 Honda Accord EX and I've been debating whether I should tear the engine down and replace everything worn and rusting and pretty much rebuilding it. Would it really be worth all the trouble and costs? Anyone have an idea of how much it would help the engine performance and lifespan?

 

How many miles are on this creampuff?
I will say that an inchassis over haul will cost around $500 in genuine Honda parts, and figure about 10-12 hours labor.
those engines are pretty tough and I've seen lots of them at 1/2 million miles, clean oil being the lifeblood of a long lived engine.