1997 Chevy Blazer Ignition switch

I bought a 1997 Chevy Blazer from my sister-in-law last week. I went to the store this afternoon and when I shut off the engine I could not remove the key. It moves back one click, but to pull the key out it has to click twice. My sister-in-law said it has been doing this on and off for about a year now. She said sometimes it stays stuck like that for a day or even two, and sometimes it's fine for weeks at a time. I'm afraid it is only going to get worse. My questions are: (1) Can I fix this problem myself, or do I have to have a new ignition switch installed by a mechanic. (2) Do I have to buy a factory switch from GM or do auto parts stores carry ignition switches. (3) About how much is the cost for the switch and about how much is the cost for labor. Thanks in advance and I appreciate any help you can provide.

Ernie H