My a/c unit fan will not come on. After diagnosing the problem I realize my contactor was not staying in place with the unit on. I manually pushed it in and the fan came on. Does this mean I have a bad contactor and if it is do I just replace it with a new one by simply removing the wires and replace the old with a new one

It may not necessesarily be the contactor holding in but something else interrupting the call for the unit to operate. Does the compressor stay on when the fan shuts off? Do they both go off? Did you check for any loose wire connections?

Is there 24 volts going to the contactor,telling it to kick in?