97 Jimmy refuse to turn off

From time to time, my 97 SLE Jimmy refuses to shut off. The key is very hard to turn. I found out that it may be due to a small black module at the base of the shifter lever with a harness plug attached to it. If I push the harness in, I can hear something just behind the dash and I am able to turn it off.

Does any one know what this part is so that I can order it? It also looks like it is a PITA to replace. I don't see any screws/bolts for immediate access.

Cheers,
P