Help me pass my safety inspection!

[cirrusman]

So here I am, my car's tags expired in June and I haven't been able to pinpoint what's failing it. Sent it to do emissions and safety. passed emmisions with flying colors but they failed my rear boots (which I had rigged with duct tape for the time being... I know I know, some of you want to slap me in the face...) so I replaced the boots. Went again and now they failed me for a leak in the fuel system. Fine, fixed that too. Went back and then it was the tie rod ends, with an advisory on my ball joints... Mph! okay, replaced them. Got the upper ball joints just in case, but didn't put them in as they look like they can hold for another year or two. Now I go today and they failed me for my lower ball joints (ah, LOWER ball joints) and strut bushings. AGH!
So anyway (and excuse me for venting here...) Here are my questions. Are the upper and lower ball joints interchangeable or do I have to get the lower ones now?
Second, what's the strut bushing? (noob! I know...) I've googled, binged and yahooed the term and they all agree on "control arm bushing", which I can get easy for $5 apiece. Is that the same thing?
Third, I haven't found a thread or DIY on lower ball joints on a w126... anyone can point me in the right direction?
Thank you kindly in advance for your understanding and your advice!