If you drop the belly pan, please be super careful. Unless your drain cleaner was 100% enzyme based it's got lye in it and the potential for serious skin and eye damage exists. If there is ANY warning about washing eyes or skin immediately upon contact, presume it's lye based.
I don't do a LOT of my own maintenance, but I have already dropped my belly pan (Had floor rot on #2, fanatic about avoiding it on "Eddie") I'm not slender or particularly agile, so I raised mine about six inches to allow easy access (and easy escape if spiders or mice dropped out!). I used three 2 x 10's screwed together with a ramp cut on one end and just rode the wheels up on them after making sure the cement floor I was on was level. Then I chocked all the wheels. Still gave me the willies being under it, so next time I'll rent some jack stands too.
Do suit up to protect yourself from the drain cleaner (and from the nasty fiberglass too).
Hope it turns out to be a small easily fixed problem,
Very Sincerely, Paula
Today is a gift, that's why they call it the present.