Ok, I have a hobbico 12v field battery. It says it needs a 12v 500mA charger for it. I have a 12v 3A and a 12v 350mA charger, will any of these work?

I would not use the 3A, it may ruin your battery.
Assuming a 7Ah battery the 350ma will charge your battery from nearly dead to full in about 20 hours. Assuming your battery isn't that low a good overnight charge with the 350ma should be enough for a day at the field.

Missileman is correct. The 3A charger might fry your 7AH battery, especially if left on too long. Use the low rate charger for a longer period as suggested.

cool, sounds good