When you go to NAPA just have them put your old battery on their battery tester. Almost all Auto Part stores have battery testers, which they should be able to configure for a motorcycle battery. This could save you from having to buy a new battery, or it will confirm you are doing the correct thing by replacing it.

Tom

Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety. Benjamin Franklin, US author, diplomat, inventor, physicist, politician, & printer (1706 - 1790)