So, a new idler arm, but what else?

I would at LEAST check stuff over. But at least an idler is not "wasted effort." That is, you are not replacing it, an having to "do things over later." If I were you I would start planning and saving for a front end rebuild. In my arthritic 65 year old lameness even I can handle this a bit at a time. In my younger years, I did one in a week end. Now, it takes me a heck of a lot longer.