Take it from someone who used to be an organic farm hand, it's rewarding work for sure but depending on the farm can be very overwhelming especially if you're not mechanically inclined. Tractors are not simple machines and seem to always need some kind of fixing up. I don't know how you are with "feeling the clutch and gears" and knowing when to shift and give it gas but it can be confusing at times.
That aside it's completely doable if you can keep your cool and not get overstimulated with everything. Key is to just take it slow and try to get that "feel" for the tractor.
It's physically very demanding too (but I'm sure you know that) so being strong and in shape is a must.
Start out volunteering at your local CSA farms, they usually take on volunteers part time for a share of food. And will almost always give a strong guy a shot at it because more than anything else, muscle and endurance is what will get you a job and opportunities to use different machines. Expect to be expected to work fast hard and learn how to use lot of different tools from fork lifts to chainsaws and everything inbetween..... farm jobs are easy to come by, most you can just show up volunteer and they'll make their decision from there.
Good luck bud 