The hydraulic control levers may be rusted in their pivot boss. It may be a toughie to get them freed up. The outside lever should be the deck control.
I didnt know 317's came with a 48" deck. I thought they left Deere with a 46 or a 50. I guess it could be a 48" retro-fit supplied by Deere. Does it have greaseable spindles on the deck?