Since you're pulling it outward, I don't know how it would fall inside? In the worst case, if it did, is you take off the 4 - 6 bolts, drain the oil (when was the last time it was changed anyways), remove the plug, apply a little silicone to the cap and bolt it back on. it's 10 - 15 minutes worth of work. If you're not at home, then disposing of the oil is a pain when on the road.
I don't think your MH is that old, but if the plug feel brittle, go buy a couple of new ones before taking the old ones out. If they feel brittle, they may start leaking soon anyway. Take a picture of the cap to take down to the truck shop or NAPA when you go.
Bill