Drive it?
But really. Inspect everything, do the basic maintenance, oil/coolant change, check belts/hoses, spark plug/wires. Maybe a transmission/differential flush, compression test to verify headgasket, Etc.
Once you do that and your engine is running strong, you can start with the mods. It all depends on what you're trying to do. Search through the forums for the upgrade list and just learn everything you can about these cars. Other than that, clarify exactly what you're trying to figure out and there's tons of people on here that will help you out.