Might as well say goodbye to it then, as alcohol is OK for glass lasers (not used anymore, AFAIK) but a no-no for plastic laser lenses. Pure isopropyl alcohol is better, but still not recommended. Touching the lens with ANYTHING is also not commendable, as it will probably get misaligned.
Anyway a non-closing tray is a different issue... are you sure you have screwed everything back as before, and the tray mechanism didn't got derailed while you were mounting back the enclosure?