I have an 83 300SD

I'm having a problem with a rough idle (especially in Drive while waiting at a stoplight).

I took a look at the idle adjustment bolt and it is the old style and adjusted all the way.

How hard is it to upgrade to the new style idle adjustment bolt?
What does it entail?

__________________
Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")