Lot of machine shops just shim the guides if they're that worn.

 

as ya'll know my complaints of incompetent German shops here I have not many choices, and when I find someone who partially know what they are doing it will cost more than the complete motor worth to do it.
so I have no choice but to do it myself.

 

I wouldnt touch the guides, they very rarely need replacing

 

It's one of those things that is hard to do at first, but gets easier the more you do it. I would suggest practicing on a junker head.