It's easier than you think to buy the wrong battery for your vehicle. Unless your current battery is definitely the original equipment, you're taking a chance by not double checking before you purchase the new battery. You can search for a certain battery, but there are a few general rules you should know before you search.
The best way is to consult the vehicle owner is manual for the correct group size and minimum rating. If this is not available, you can look up the vehicle make, model, and year in a battery application guide and note the recommended group size and rating given
Sealed batteries are known as maintenance free batteries. They are made with vents that (usually) cannot be removed. A standard auto or marine maintenance free battery is sealed, but not fully leak proof.