Tumbler question

[ned2683]

so my key would not turn in the ignition. i tired until a spare broke (not inside the ignition tho). i think bad tumbler. now i am not freaking out yet (i was this morning tho). i did soem reading on this site. and i don't think i can afford the cost for the new parts so my questions are:

1. would a tumbler from a 78 300sd, fit a 84 300sd? seeing that i have no money and i don't mind having 2 sets of keys.

today i will try to:
1.turn steering wheel while turning key
2.spray in lube while wiggling/turning key
3.apply vibration on the key

might be a coincident but today the temp went down to 2*F. the coldest so far i think. could it be that soemthing is simply "froze" inside? i sprayed in some deicer and hopefully if it is frozen it will loosen when the weather gets better. anything i am missing?