(ET) Lost all forward speeds on E12

[Richard Zachary <njcfsa earthlink net>]

Had problems a few times with moving the throttle forward and getting no 
response or a quick jump in the power usage needle but then nothing.  
Now I nothing at all going forward but reverse works fine.  Had to 
finish yesterday's mowing in reverse only.
Also previously the throttle was jamming so a drop of lubricant on the 
controller by the first switch solved that.  My guess is that the first 
switch became worn or damaged by my pushing past the jam (before the 
lubrication). 
Would the first speed switch be enough to account for the loss of all 
forward speeds? 
I have an old controller (for parts) and guess that replacing the first 
switch might be the way to go.
I am a complete novice and am just trying to go on common sense. 
Any advice from someone with experience would be greatly appreciated.
Thanks,
Richard "Zack" Zachary