You would need to ride the bike to the store. If you want to have them check for charging voltage.
When you have it running, and have the headlight pointing at the garage wall, can you see it get brighter when you rev it off idle. This will tell you that your charging system is at least putting out some voltage.
No, just take the battery no need to take the bike, do not trust their peception of an "OK" charging system, just have them check the battery & nothing else. Motorcycle's & cars are 2 different things, a diganostics test for a car may not work for the bike. Here is what to do since you sound unsure :
1) Charge battery
2) Remove battery
3) Take to auto parts
4) Have them load check it, twice to be 100% sure (have had a bad battery past 1st test before but not the 2nd)
5) If it fails, buy a new battery, but keep in mind that they probably dont sell gel or sealed battery's there & if you purchase the liquid acid type it should only be used to get you out of a pinch or Temp. use.
6) IF its good, trouble shoot the R/R & stator when you get home, there is a procedure in the manual on chapter 16 section 7 (16-7) to do this.
Clear ?