newbie with an OLD Gator

Hi,
I am helping my son with an older 1996 Gator Gas 6X4
We are simply trying to resurrect this old gal - and make it safe to use around the "gentleman's" farm in Northern Virginia.

This old beast has three electrical issues:
1.) someone has fiddled with the coolant temp switch that controls the electric fan and has disconnected it
2.) the charging light is on all the time - and of course, battery is not charging
3.) the oil pressure light is on all the time. (plenty of oil and appears to be an indicator issue)

Where would I locate the engine ID tag - there is supposed to be differences based on the ENGINE S/N -?

Suggestions on how to troubleshoot (without simply replacing parts) for the charging system/regulator circuit

Thanks in advance
-J-