The big issue on the 6 cylinder motor is access.
They put the pre-cats on the exhaust manifold in the way.
Otherwise the idler arm bushings would be easy to change.
Remove nut, remove bolt, knock out bushings, replace everything.
Just not sure what the access issues are on the V8.
Someone here must know. These things are a common wear item.
You could probably tell just by looking at it.
If it can't come out the top, the consensus technique is to cutoff the bolt head, then reassemble with the bolt 'upside down'.
1986 300E 5-Speed 240k mi.