Can you put any tuning machine head into any guitar?
depends, tuning machines have different sizes. if it bigger than what's already there you would have to drill the holes. i don't think there is a way to accomidate smaller tuners.
You usually have to drill; outside of that, it's just a matter of getting 3x3 (gibson style) or 6 in-line (fender style) tuners.
I'm planning to replace vintage style fender tuners!