Wmagel, Welcome to the forum.
To open you batter draw, spray penetrating oil in the latch track. Spray from the back and underneath the latch mechanism and work the handle and it should open.
Remove the batteries from the compartment. Dissolve a box of baking soda in a gallon of warm water and with a brush scrub everything down. You may have to do this a few time to neutralize all the acid. Rinse several times and let dry. If you have any rust spots scrape the loose rust with a steel brush then treat with
Ospho. Once the Ospho is dry prime and paint everything. While waiting for the paint to dry wipe down the tops of the batteries and cable connections with the baking soda solution being careful not to get any in the battery cells then replace and connect the batteries.
I have 4-6volt Interstate Workhorse batteries that I put 4 oz. of mineral oil in each cell. This puts a 1/8 layer of oil in each cell and still allows you to use a hydrometer to take specific gravity readings when necessary, just be sure to get the hose below the oil to the top of the plates. I used 3-16oz. Bottles of mineral oil for the whole job. I bought the oil at Walmart for about $1.60 for each bottle.
That's it!! You battery corrosion worries are over.