transmission on scag walk behind won't engage in gear

[andrew's lawn care]

hi. got this scag 36 with Tecumseh tranny. I finished cutting an overgrown lawn today, then the plug under the electric clutch fell out, as well as the transmission just started making an awful sound, like there were gears grinding. also, the spindle below the tranny is really loose. not sure how to tighten it or if I should. none of the gears work, so I'm stuck using the push mower, and all dealers are closed till Tuesday. anyone know what's going on? do I need a new tranny? appreciate any help.