Do you mean the older round type solenoid?
No need to fiddle with yer nuts
To open it up remove the two screws
Unclip the cable from the brace
Cut the outer sleeving back to allow you to feed the yellow/red and green/red wires
through the black plastic top section as you withdraw the 'cup'
Having said that, your options are limited when its opened up
and there's a test you can ( should?) do first.
The resistance between the Y/R and G/R wires should be about 3.5 ohms
if you get a dead short or significantly higher readings then the coil may be knackered and you'll need a new one
just opened one of mine to show you