2000 GMC Jimmy Intake Manifold

The most important thing to do is make sure the leak you can see is the only place it's leaking. You don't want any of that coolant getting into the crankcase.

I would change the oil & visually inspect the removed old oil. If it has a milky appearance, you could suspect internal coolant leakage as well & should have a qualified mechanic verify.

If the old oil appears normal, zero in on the source location of the leak. You likely wouldn't need to replace the thermostat, belt, or cap, assuming you're pretty certain the leak is from the intake manifold. Clean the areas that are wet or dirty, run the engine until it's hot, try to find the location of the leak. That will determine any further hypothesizing.

But the main thing, if you suspect the intake manifold, is to be certain it's not getting into your oil, and do that as soon as possible. That can damage your engine pretty quickly.