Ok, your going to get lower mile per gallon when driving that car with a trailer, it wasn't built to haul trailers. It really depends on how heavy the trailer will be, make sure you load the trailer to have the larger portion of the weight resting on the axle, and there is substantialy more weight in fron of the axle than behind. This way, you will not be putting ht full weight of your stuff on the rear of your car, and you will have the trailer carrying most of the weight, you just pull it. If you have to much on the rear end, it will want to pull up and off the hitch, just be careful. Don't use overdrive, use Drive, Overdrive is a gear and setting in your trans. that uses a lowe fluid flow to increase fuel economy, your fluid is what lubricates and cools the trans. I have seen people ruin a tranny on 1 trip because they hauled a trailer in overdrive.
Anyway, your question. Figure on 20 mpg. But you may not even get that depending on how much weight there is, how often you stop, what yout speed is, there are alot of variables.
Take the miles your trip is, divided by the average MPG you expect to get. That is aprox how many gallons you will need.
Albuquerque to Birmingham is about 1250 miles
1250 / 20 = 62.5 Gallons used
To be safe figure on 75 - 80 gallons
80 gallong at 3.00 a gallon (Safe guess)
$240 for gas, double chec everything beforehand, but this is a rough guess.