1991 Mazda Navajo Non-battery starting problem

Hello,

I recently bought my friend's 91 Navajo and, as soon as I bought it, it started having problems not starting. Twice, it refused to start, but, when I came back to it later, it started without getting jumped. Now, it just will not start.

When I turn the key, there is an almost buzzing noise and then a pop.

I had a guy from advanced auto parts check the battery, and the battery is fine. I removed it and cleaned it just in case.

People have suggested to me that it is the starter or the connections.

From the little information I can provide, what seems like the best course of action? Should I just go buy a starter and attempt to put it in myself?

Please help. I cannot find a job until I have a working car. Thank you so much in advance.