I have had no problems here. They are always nice.
You will go to the rental counter across from baggage claim and get your keys and contract. No aisle.
They may or may not have different cars to switch to. It is a small operation.
I always have to take my paperwork in and drop it off at the rental desk with the keys. There is no express check in. I once had to use the key drop at the desk and get the receipt emailed. Again, no problems.
Make sure that you are set up to get receipts by email if you have to have a receipt.
If you are worried about charges for additional damages that you did not do, take photos all around the vehicle making sure that the airport is in the background. Also, give it a good going over before leaving the airport and walking back in to tell the agent before you take the car if you find damages. The open air lot is dark at night, and you may need a flashlight to look over the car well.
You can fill up at the Casey's about a mile from the airport but it does not stay open all night. I am not sure when it closes but it opens just early enough for the first flights of the day. Alternate fueling is at least one exit away on the interstate.