You should not lose too much coolant on the IACV swaps. Obviously do it without engine running and relieve coolant pressure by removing radiator cap.

Also, after the IACV install, bleed & refill coolant level. I know you were not confident in this process based on your thread, but it is easy. Ratchet, extension and 12mm socket is all you need. Go to thermostat housing (where lower radiator hose connects to engine)and locate the bleeder port. Loosen that counter-clockwise, opening it one full rotation. It helps to put a rag or white paper towel at base of this area. Then, put coolant into radiator neck until it reaches the neck and watch bleeder port, it will bubble out coolant and/or spurt. Wait until the coolant comes out with no air bubbles and pours out smoothly. Close the port clockwise rotation using regular force snug, DO NOT overtighten or you will break it off (seen someone do it)...use force much like brake bleeder port. Continue to pour coolant slowly into radiator neck until fluid reaches neck level. Install radiator cap and run engine until coolant temp needle fully warm. Then, proceed to perform setting base idle, reference my DIY sticky.