So last night I heard an animal in my attic, scratching and clawing
vigorously on the wood attic floor.

Not really sure of the best plan of attack here. Don't know what
animal it is yet.

A walk around the house with my friend didn't reveal any obvious holes
for entry.

I just bought a havahart trap for squirrels etc.

Let's say I set it up near the attic door opening.
Do I just check it every day for a catch?
Can I hear a catch?
Is it in any way dangerous for me once the animal is caught?

How do I plug the hole of entry when I don't know where it is?

Should I just call an exterminator?

Thanks!