You're in the Mecca of R/C racing, so I would strongly suggest getting yourself a personal transponder (lap counter) since I doubt they have handouts at the races due to such a high volume of participants.

Get the DX3.0. The DX2.0 lacks exponential adjustments which come in handy for dailing in/out the sensitivity in the throttle/steering. Plus it has the 3rd channel, so it's easy to plug in your transponder. Otherwise you have to use a splitter and then you'll have a rat's nest of wires to deal with.