Is there a way to pressurize my Expy's cooling system without running the engine, so that it's cool to the touch and I might hear a hiss from the pinhole or crack?

Are there any tricks to replacing the thermostat or water pump? It seems pretty straight-forward to me.

How do I flush/fill/bleed the cooling system properly?

My truck is a 2000 Expy 4.6L XLT 4x4 6-code with 175k+ on the clock. It's got dual air.

In the next week, I need to find a radiator leak, then replace the factory-original thermostat and water pump and finally flush/fill the cooling system.

I think the leak is in the upper-passenger corner of the radiator. The coolant residue on the surrounding areas is convincing. But I can't eyeball the leak, which explains my first question

Question #3 is born of ignorance. It was probably 1983 when I last installed a Prestone Flush/Fill kit and that car had a good ol' pressure cap right in the middle of the upper radiator tank. But my head fills with questions when I contemplate the overflow bottle on my Expy.

THANK YOU