BLI GG1 Truck Replacement

The truck came off of my BLI GG1 while running on the track. Fortunately I
recovered the plastic post, spring and nut. I don’t know how to hold
the nut in place to reattach the spring, post and coupler. There is almost no access to the nut. I don’t want to start disassembling anything before I know what to do. Is there any
easy technique to do this?

Thanks Doc

The best advice I can offer is, send it back to Broadway Limited and let them do it. You could end up voiding any warranty if you attempt to repair it yourself, break something else in the process, and wind up with a destroyed engine.