First off, you got an absolute steal on that bike. I will take that all day everyday.
Second: As far as the old battery, your use for it is this: You can go to walmart and buy that same battery, but they will charge you $15 more if you don't bring back an old one. Keep it, bring it with you when you get the new one.
Third: I can help you with the spare bowl, cheap. You can call me if you want as my number is in my thread, or just PM me. If you don't mind one with the drain tube (coming OUT the bowl) with a little bend in it I'll hook you up for free as long as you pay for shipping.