If you leave from the airport with that overstay there will be no problem, you will just be charged the usual B500 per day and have that stamped in your passport.
That you left your passport renewal too late will be looked at as your problem, there is no exemption for your situation (unless is was just one day, maybe two, if you're very lucky).
Edit: just re-read your OP, my apologies for misreading your situation. Re the overstay, unless you sort it out with Immigration before you got to the airport, you'll still have to pay the fine.