The battery has little leeway in size but stock is 14AH. If you look at the front of the battery, the - terminal is on the left and the + is on the right.
I prefer to get batteries in a store. You might spend slightly more but you do not have to worry about shipping and if your battery goes bad and is under warranty, you drive to the store and get it replaced.
You also get a credit for the old core.
The ride IS the adventure. The destination is just to get gas!