It is basically impossible to repair the pod without removing the dash. Others have done it by cutting a hole in the dash (!!) and then using a dash cover to hide the hole.
The other option is to use a wire or something to force the pod open so you get cold airflow out the center during the summer, and plug the vacuum line. I have done this job 3 times on a 124 chassis but never on a 123. On the 124, the first time it took me 10-12 hours total (replacing ALL the pods while the dash was out), but by the third time I could do it in 4 hours.
HTH,