With the deck off, and the gas tank empty and the
battery removed. I would take a chance
and hoist the front end up until the underside
of the tractor was accessible.

In my case I have a 2 post Bend Pac auto
lift whose 4 arms can reach the mower and lift 6
feet high.

I removed hood and sides all as one assembly.(six bolts) and was barely able to reach between gas tank and the lower part of the plastic dash panel to get to nut and was able to remove the nut and the broken part of the bolt. I held the idler plate with the new bolt along with the washers, spacers and other hardware in position with a small jack and was able to get the new nut on a couple of threads and then placing an offset 9/16 wrench over the nut to hold it from turning I tightened it from beneath. It was a bear of a job but it's up and running again.