Good thoughts to get organized.
If you can, organize a group dyno day - that can spread the cost around, be a lot of fun, and keep things transparent in the class.
Look through the dyno procedure we posted, and make sure you follow that - get the car warm, make sure the shop is using SAE correction, etc.
At the same pressures, and tread depth, I'd expect the RA-1 and RR to dyno similarly. Leave yourself a little more headroom, if you using full tread RA-1's as your baseline. I don't know how much tread depth will affect dyno readings (I'll work on checking that next time I'm on the dyno).
Most of all, go through your car before you go - plugs good? Cap & rotor good? Fuel filter reasonably recent? AFM wiper track not worn through? Etc. - you want the car tuned up to give you good readings.
I would certainly plan on doing AFM tuning if your renting the dyno for an hour or so. Just go in small steps ( 1-2 clicks at a time). Look at the AFM tuning thread for more details. Richer = CCW.