Where is it leaking? When they said the compression test was fine did they provide the particulars? What each cylinder was reading?
Have you replaced the plugs with stock (606's) yet? Because before you invest in the motor, you'd want to make sure it's worthwhile. Bottom line is if you plan to mod and then attempt to drop pulleys, the safest way to do so is by making sure everything mechanically is sound and up to par. Then have it tuned or scanned for a baseline, then tuned with mods, when good then, THEN... Drop pulley. There is no standard as to what you can do (mod) and then drop.
Anyways, you will pay slightly more than they would for parts and save on the biggest cost which is labor if you do some homework, gather all the tools and parts and roll up your sleeves to get dirty. For what you'll pay them to change the LIM gaskets, you can do that, the valve cover gaskets, tranny filter, gasket, fluid, engine oil, filter, fuel filter, plugs, wires and more... But I wouldn't do it if not knowing the engine was ok.