On the idling issue... 2 strokes definitely can idle. My 125 will sit there just barely turning over for as long as you want it too. (Well, ok, if you left it for more than a minute it would probably load up and quit.) Some people feel they get better throttle responds when they are tuned so that their bikes don't idle. I haven't found this to be the case with my bike, but you may find different. Adjusting the idle is real easy, I'm not sure of the carb on the CR, but there should be a on the side of the slide bore that screws in and out... probably has a spring on it. This would be your idle speed control... in increases the idle, out slows it down. I'd try running that screw in a few turns and seeing if it will idle. If the bike starts and runs fine other than no idle, I'm sure its just set too low.
Other things to know... burn good oil, make sure your jetting is setup pretty good, keep the tranny oil and filter fresh, burn good grade gas, and HAVE FUN. 125's are a BLAST! Good luck!