first off, thanks new pals for the quick reply! I haven't found that "go advanced button"? But I do have the JD GX 255 drawings in jpg format on my 'desktop'. not sure how to import them to you.
Well, obviously I found the missing "go advanced button. Duh!
So, when I crawled out from underneath the tractor last evening I guessed that I should start at the rear, and get the belt over the fan and proceed towards the front. The spring was off but I see where it attaches to the 'arm" part #11 with the other end of that spring to the cross bar of the frame (not shown in the drawing, of course).
But, the rub is now having the rest of the drive belt on the opposite side of some steering linkage from what I recall. So, that's where I left it not wanting to tear anything apart without knowledgeable advice.