you have the tcu correct?
look for a shop that works on Mercedes euro cars , they are all similar, you could call a few performance shops and see what they would charge. . you can change the tcu, it is under the carpet on the pass side, just unbolt the 307 ,,unplug the 307 tcu and plug in the 327,, tag them as they look the same.
who did you get the rear and the tcu from?,
to do it your self, you need a lift, ----------
1 drain the oil
2 take all the arms loose, not the lower control arm,
3. take the brake caliper off the rotor, tie it up.
4 with the shock loose from the lower control arm
5 remove the axle nut at the rotor
6 pull the rotor down and to the left or right so the axle will come out of the rotor
7 remove the bolts on the driveshaft center bearing let it float
8 remove the bolts on the driveshaft flex coupling, pry the drive shaft out of the diff.
8 put a brace under the diff or have someone hold it up as you remove the two bolts at
the rear of the diff, remove the bolt at the front of the diff.
9 remove the diff.
10 reverse the steps to reinstall the diff. use only the oil recommended by unatrx

note the srt6 and the limited use two different yokes. see here

https://www.crossfireforum.org/forum...ferential.html