It's worth noting that, for a session, stereo recording isn't strictly necessary. You can, therefore double the recording time on your discs by using the mono recording option.
The information is in the manual, so I won't waste space on that here. I have the MZ-R70K, which they are selling off cheap now that the new one is out. I've not looked into the difference too closely, in case I convince myself I should have waited!!
A cheap tieclip condenser mic will probably be more than adequate - I'm assuming that your reason for recording the session is to learn the tunes afterwards?
If not, ignore everything I've just said!!