Sounds to me like your linkage is the problem. To check it you'll have to have someone in the vehicle and raise it in the air (to have wheels off the ground) disconnect the linkage from the transmission. Have the person in the vehicle apply the brake and shift the transmission at the neutral safety switch. If it shifts into gear you need to change the linkage, if not you'll need to have the transmission checked.
Answers & Comments
Sounds to me like your linkage is the problem. To check it you'll have to have someone in the vehicle and raise it in the air (to have wheels off the ground) disconnect the linkage from the transmission. Have the person in the vehicle apply the brake and shift the transmission at the neutral safety switch. If it shifts into gear you need to change the linkage, if not you'll need to have the transmission checked.