I'm the Chief of a small town/rural department. I'll try to answer your questions as best I can.
1st as far as employment goes you are not required to leave work for a call. If you can GREAT that's the biggest problem volunteer departments have is daytime personnel that can respond. However it's entirely up to your employer as to weather or not you can leave during your working hours. There are no laws on the books to protect your employment if you do leave either.
2nd training. Each department sets their own SOG's (standard operating guidelines) and define what training is required. Typically the larger the department the more training is required, for example a municipal department that runs mostly structure fires, vehicle crashes etc might require more training it those areas than say a rural department that fights mostly grass/brush fires.
On my department this is what we require:
NIMS: IS100, 200, and 700 (these can be taken online and are required by ALL agencies)
Wildland fundamentals -- 16 hours
Wildland skills -- 16 hours
Volunteer Firefighting Practices -- 32 hours
Structural Firefighter -- 48 hours
Hazardous Materials Awareness -- 8 hours
Basic Vehicle Extracation -- 16 hours
Advanced Vehicle Extracation -- 12 hours (not required but encouraged)
CPR/First Aid (Emergency Medical Responder is not required but strongly encouraged about 60 hours)
Basically you can count on needing at least 150 hours of formal training not counting on department specific training such as how to operate that departments equipment and what their procedures are.
I don't know what area of the state your are in but I can tell you that Volunteer departments are in DIRE need of personnel. My department at this time is down to 10 volunteers and 3 of us can retire at any time (I hope to in the next year) so please if at all possible volunteer. Even if you can't respond during working hours you are needed.
It's the greatest job you will never be appreciated for.