The easier method is to go into interp.c and find the grant command, change the level to use from ML to 1 then login. Use grant self 101, 102, 103 etc. until you have all the groups you want then change the level of grant back to ML.
I haven't had a problem with imm powers sticking with the pfile using the method I described above. Played with AN quite a few times over the years and have created a number of immortal characters without any negative affects.
It's a pretty sloppy system in the first place for creating an admin, should just be rewritten.