Record Series / Single Ep question

I've been a tivo user for many years and just recently got myself a HR21, so please excuse me if these are silly questions.

With my tivo I was able to look at episodes of a recurring recording and also record non-scheduled eps manually (i.e. if I wanted to record a rerun of a show that was set to first-run only). I was looking at the episode list for Psych, which I have a First-Run recurring recording set for, and highlighted one ep that I had missed and hit the (R) button. When I did that it set the single recording, but it deleted my recurring recording from the prioritizer!

So, how do I have Prioritizer recording but also add the occasional re-recording?

Second, semi-related issue: I manually added a show yesterday, and it conflicted with 2 series recordings at that time. I had it overwrite Recording 1. This was a HIST recording, so I know it will be rerun later that same night. Should the prioritizer have gone through and rescheduled that series recording for me? I didn't see it. Does it just take a while to do (I know Tivo needed to reshuffle the recordings daily for that to happen).

Thanks for answering my newbie questions...