Today I replaced a leaking tubeless valve stem without removing the wheel on my GV 250.
I used a c-clamp to squeeze the tire enough to break the tire free from the rim, then pushed the tire to one side, reached inside the rim and removed the broken remains of the stem, then wet the new stem with WD-40 to lube it and popped it in place pulling it gently with a vise grips clamped onto a metal stem cap so as to not mess up the threads on the stem.
Inflating the tire took a little jockeying of the tire bead to get it to seal on the rim, moving the tire around until it starts to hold air.
I use a Pep Boys 12-volt pump to inflate my tires, powered by my battery charger.