Running a RIMS will be easier than single infusion mashing... and trying to hit temps. At least this beast will hit temps for you.
I run a HERMS, and have studied both. What you are going to find is that it should be easy to maintain temps with the temp controller (where are you measuring the wort temp?)
What you will aslo find is that each system has a personality that only through use, will you be able to understand. Your system may have a temp differential (between the RIMS heater and the MLT) due to normal heat loss during the transfer.
What you NEED to do is fill your HLT and MLT with the same volumes that you will be using when you brew. Then, run the system as you will when you are mashing and sparging... this is a dry (wet) run. This will familiarize you with heating times, point out any leaks and give you an idea of your systems specific "personality". Flow rates, heating times, and any temp differentials that you may incur when actually brewing.
Your first brew will be an "experiment" of sorts... take good notes. Temps, times etc... so that you know what to expect in later brews and so that you can correct anything you deem as a problem.
#1 though is the dry (wet) run... you have to do that first IMHO
Preheat your mash strike water to strike +10 or even +15F to preheat the MLT. When you do your dry run, take note of how quickly the strike water cools to the appropriate strike temp.
Mash in... stir thoroughly, take time to break up any dough balls and such. Assimilating the temp at this point is not a HUGE concern since you will be starting your RIMS recirc shortly. This will help to equalize temps in the mash.
Start the recirc. (are you going to recirc continuously and control the heater only?) I recommend recirculating continuously, that is how I roll... You can do whatever you want. But, really the less insulated the MLT, the more you want to recirc and heat anyway to reduce cold spots where heat is lost (bottom, top and sides of a SS keg).
During the mash, heat your HLT water to your sparge temp (168F or so)
Monitor your RIMS temps and the resulting MLT temps... see if there is a differential, and take note of what it is. Most controllers allow you to set a differential or dead band... play with this during the dry run to see what is most appropriate for your system.
Mashout... take note of how much time it takes to reach mashout temps in the MLT... this will be evident when the output of the MLT is the same temp of the input to the MLT (168F or so)
But, again, please do a dry run... this will save you MUCHO headaches on brew day.
This would be a good brew...