mercury 40 stuck in forward

[gillgetter]

Hello everyone-Great site you have here. I have a problem with my pontoon.I was going to put my boat in reverse to clean some weeds off my prop,but it just revved up in nuetral.Cleaned weeds off by hand-still no reverse.Brought it back to dock-restarted-now I only have forward-no nuetral or reverse.I did not think you could start a motor in gear.Shifter feels the same going into f/n/r and will only start in nuetral position,but it surely is in gear because it tried to drag my dock away.I dont know if its something in the motor linkage-the control box-or a broken cable. Motor is 92 merc 40 4-cyl-I believe the control is a quicksilver commander 2000 from what I have seen on internet. Any troubleshooting advice or ideas would be greatly appreciated. I was going to try changing the cable first. How diffacult a job is this,as I heard that control box is hard to take apart. -Thanks