A simple google search will answer a lot of these questions for you actually. Just make sure and read everything you find with a grain of salt. Check more than one resource to make sure that the information you're reading is accurate. This is especially true for forums...where someone biased might post a poor report of a bike without having any previous experience on it.
I am not positive, but I believe the CRF 250 F was made in 2003, and one other year (that I cannot remember). I would suggest going into a Honda dealer, and asking them to look it up for you.
I believe that the 250F model has a lower maintenence schedule than the 250R (logically speaking). However I haven't heard much about it. I have heard quite a bit, though, about the 250R's having some pretty particular needs. I have never been on the 250 F or X model, but have been through the thick and thin with a friend who has the CRF 250R model...she hasn't had the greatest experience with it maintenance-wise.
I'd also suggest that you pick up a newer model (2000-2003) Honda XR 250 if you can't find the CRF 250 F. They are not that great on a track, as the suspension can be a little soft. On the trails, they really shine! The power is very predictable and steady, and it is fantastic for learning on. Also, once you do learn, it will still have enough power to keep you interested. They are really fun out in the gravel pits and woods!
Maintainence is also going to be super low on this bike. You fill it with gas, check and change the oil regularly, and that will pretty much be it. They are extremely reliable as long as you give them a little care.
Another good idea, if you haven't done so already, is to go to the dealer and sit on the bikes, and ask as many questions as you possibly can.
Hope this answers a few more of your questions!