New odyssey owner here

timing belt is at 105k miles (the maintenance minder will tell you), for the power steering, Honda actually recommends having the pump push the fluid out, then refilling the system. Most of the transmission issues are for the previous generation van. If the van is new-to-you, I'd change all the fluids (oil, power steering, brake fluid, and transmission) and filters (air, oil, cabin). Plugs aren't due until the timing belt is changed, effectively (they are iridium tipped - ours actually looked pretty decent when I changed them at 105k miles). Make sure the struts are in decent shape, and check the engine mounts (if it's a model with VCM, the front seems to go early and is expensive - for the others, the side and front seem to go - we had both fail on our van - since we don't have VCM, they are inexpensive, and not a big deal to replace.)