The least expensive/best sounding setup you can buy are Church Audio CA-14 cardiods with a simple battery box also made by Church. See "Retail Space" below. However, be advised that build/delivery times for handmade gear can be long, so be sure you have enough time to get this made before you have to go to this show.
Any setting on the deck that suggests that it does something automatic - limiters, auto-level-adjustment, etc - turn that off.
Connect the mics to the battery box, connect the battery box to the deck via LINE-IN and let it rip. Record at at least 24/48. I can't tell you where to set your levels, but the general theory is "conservatively" meaning as long as the peaks are at or near -12dB on the level meter, you can always raise them in post-processing.
I highly recommend going to a local show or something you don't care about and practicing before you try to attempt recording the thing you really care about with a brand new untested rig. The chances of something not going as planned with brand-new equipment one is not familiar with are very, very high.