How easy/hard is it to do all that. How much time? Skill level?
It went pretty well for me. Took a bit over an hour on the first one - but only because I was super paranoid and triple checked everything, referring to the photos constantly. Second one took less than half an hour at a relaxed pace. Minimal soldering skills, a basic soldering iron, some solder, and a wick.
I tried the polyfil thing - I thought it was a pain. Had my wife supporting each driver after I pulled it out. Gave up after awhile. Never have finished that little project

I don't think I would try putting no rez in unless I tilted the speaker over and got a good work area - tight quarters and a true PitA.