If a gas station is sending out wires by Western Union, are they now a MSB?

more than likely ...

They are probably an Agent of Western Union. You'll need to have a conversation with the customer (better yet, a site visit) to determine the extent ...

That's how I found out they were doing the wires. I was there getting gas, and I saw the Western Union sign hanging in the window. I am also going to call them and see if they are cashing checks too. I didn't see any signs for check cashin.
So if they are an agent for Western Union are they a MSB or is the Western Union the MSB?

They are an MSB but do not have to register with FinCEN (as long as they don't do anything else such as cash checks) since WU is registered. You should ask them for a copy of their WU agreement.

Western is the MSB - they are merely an agent of Western Union. If they are cashing checks totaling over $1,000 for one customer in one business day, they are themselves also an MSB. If they are doing this, you should see multiple third party checks deposited into their checking account and also you should see cash withdrawals made to fund cash in the business for cashing the checks.

Good luck!

Western is the MSB - your customer is merely an agent of Western Union. If they are cashing checks totaling over $1,000 for one customer in one business day, they are themselves also an MSB. If they are doing this, you should see multiple third party checks deposited into their checking account and also you should see cash withdrawals made to fund cash in the business for cashing the checks.

Good luck!