I got lessons from my boss who is the back up farrier for the local one when she goes on vacation or something. I just did my first round of unsupervised trims and it was great. As long as your horses have normal hooves with nothing seriously wrong with them then learning to trim them should be very easy. I think that it is something everyone should learn to do, just in case, but of course that won't happen. :)
Just want to say though, that when it comes to your tools, you DO get what you pay for. Cheap rasps don't last long and cheap nippers dull fast. You don't have to have the top of the line tools, but not the cheapest stuff either. Good luck!!
Proud owner of ~Mana: 6yo Arabian gelding~Pearl 13yo Arabian~Danzer 14yo Arabian mare~ Tiny mini filly