I have a 1995 JLX 16 valve, automatic 4WD Sidekick (bought it last week

and last night, for no apparent reason, the key refused to turn AT ALL in the ignition. I called a tow truck and the operator got it running by hitting it really hard and turning the wheel.
I tried the same thing this morning to no avail, except I did get the key into ACC and tried the starter but nothing happened. No sounds, no nothing, so I took it back out and was unable to ever get it to turn again.
What do you think is wrong with it? Can it be fixed simply or do I need to change parts?
Any and all help is greatly appreciated.