Engine isnt worth dick unless you work it with lots of money. Even then it will need lots of time and you can probably spend less time doing a H22 swap on the car along with less money and be way more reliable as well.

As far as small DIY stuff, upgrade the engine grounds, get newer plugs and wires, check your cooling system including radiator and all fluids, check timing belt, run an injector cleaner, upgrade the interior speakers.......