I can only speak for my very short experience at a 1LT in the California National Guard -- I have only drilled 1x since my commission in Feb.
Your initial training, "BOLC" or Basic Officer Leadership Course is 3 wks, 2 days in TX. You have to do this within 2 yrs of commissioning but sooner the better. You will also have "AT" (annual training) of 2 weeks.
For my "clinic job" in the ARNG, I work at the state headquarters and basically give medical clearance to soliders for deployment. No treatment rendered. Every unit is different, I chose to be in this type of situation since I had no military experience and was told this unit was particularly a good starting place for a military career.
Re: deployment, I think there are a lot of different rumors floating around. I have heard max deployment is 6 months for a PA in the ARNG. I have found so far that the Guard will accommodate my schedule as far as further training. You can always ask for a make-up date.
The loan repayment or cash bonus are nice but you have to do this because you want to serve. Everybody can tell if you're just there to get the cash. It's not worth the time or sacrifice if that's why you are joining. I joined because I wanted the best of both worlds -- a civilian primary care job and military experience. I wanted the training the military gives plus I really wanted to give back to those that have allotted me the freedom to post on this forum.
Let me know if you have any questions. Good luck with your decision.