Breaker panel question

I am going to install a new piece of wiring from my transfer switch to the breaker panel. The white wire from the transfer switch is connected to the metal bar (bus bar?) by a screw which has a damaged head and is proving difficult to remove. I can probably drill it out but the threads in the bar may be damaged. My question is, does it make any difference which UNUSED hole in the bar I use to connect the wire to. If the threads are damaged, I just want to use a new hole if possible. There are two white wires connected there, so once I get it loose can I reconnect it elsewhere.