Should lose very little if you leave it on the kickstand. Also remember that the tranny holds less than a quart. Approx 24 oz. + or - a couple. If it's been awhile it never hurts. I'd still change it the next time the primary is due....just to keep it on the same schedule. I agree with xxx, just top it off.
Do you have the owner's or factory service manual? If not, at least one of them is a MUST HAVE if you want to really get to know the ins and outs of your bike. You can order them at the dealer.
My first choice would be to go ahead and replace the trans fluid. However, if you want, you can drain it into a clean container, and then re-use it after you're done. Or, as others pointed out, you'll likely lose little to none if you keep the bike leaned over on the stand.