Engine Swap

I have an 85 Prelude and its very old w/220k mi on it. However it was given to me as a gift and i have about $500 to spend plus im working. I wanted to put a new engine on it because the stock one is old and only has 100bhp, so I figure i just put another engine on it. Also it is a light wieght car, 2171 lbs. Any suggestions on what to do or how much it will cost? And should i do a self installation or have someone who knows do it?

Another thing, would it be worth it to do the swap or rebuild the engine with mods?

Would really appreciate the advice. Thnx!

[The attachment is a pic of an 85 lude. My prelude looks like this except its metallic midnight blue w/ eagle rims.]

pic