Steve,
Welcome! 
You can replace the bellcrank by making a small hole in the bottom of the wing to gain access to the nut on the bottom that retains it, then open up the top enough to snake out the existing bellcrank.  Hot stuff/solder some thin wire about 3' long to the existing leadouts so that when you pull out the old b/c, it will pull the new wires through. If you order a control system from Tom Morris (@Stunt Hanger Hobby) and specify that it's for an ARF Nobler, then you can hot stuff/solder the new leadouts to the ones you just pulled through, then pull the new ones back out of the wing as you slide the new b/c back in.  Add an additional plywood top mount above the bellcrank so span between the adjacent ribs. adding the rest of the linkage is pretty much per the kit instructions.
I'm sure others will fill in the blanks!