Ok i'm pretty new to this so bear with.
Few questions really.
1. Can you run a mic/vocals through a guitar amp?
2. Is there a "best" way to set up all the amps and everything so the whole crowd can here everything (we're talk 30-100 people bars here)
3. Is it possible to do smallish gigs without a PA? just amps?
1. Yes, but it doesn't sound very good and having a single set of speakers will mean that some if not most of the crowd won't be able to hear you very well. Also - there will be no means of monitoring for the vocalist.

2. Unless your stage is huge (like theatre size) where you put the amps won't matter so much. Tilting them up can help projection as would putting it on top of some milk crates.

3. For any crowd size apart from a tiny café you would need a "bare bones PA". That is a microphone, mixer, power amp and at least two speakers.

Fender Standard Jazz Bass
Artec Matrix Pedal Tuner
BBE Optostomp
Boss GEB 7
EHX NYC Big Muff
Ashdown MAG C410T-300
Torque T100BX
GAS-ing for:
Boss SYB5
Behringer Intelligate IG9
Pretty much....

Could I get some more talent in the monitors, please?

I know it sounds crazy, but try to learn to inhale your voice. www.thebelcantotechnique.com

Chris is the king of relating music things to other objects in real life.