The only way I know, is to trick the SKREEM into thinking you are using the key in the door. So, get into the wiring from the driver's door and wire your lock/unlock lines from the new module to those wires.
This way, the SKREEM takes it from there, and the alarm won't go off, etc. as the SKREEM "thinks" you are putting the key in the door and locking/unlocking in an "approved" manner.

One way is to tear the dash out and get to the connector on the SKREEM, but I THINK C228 is under the dash on the left hand side - easy to get to if you drop the underdash.
Just keep in mind that the SKREEM is located behind the speedo to make it hard to get to, sure, but it is also up hign, surrounded by plastic, which gives your FOB more range, so placing your module up there might be a good idea, even tho it seems like a lot of work to get in there, to me, anyway.