This Document describes steps i took to change the AA, SDK, DW and SRSS SCOM passwords. Please look it over, test it in your lab and comment on the value of the walkthrough. I must say the SRSS part got me stuck and took a couple DPM restores to get through it. I did not have any IIS instances as other walkthroughs suggested. I am running SQL 2008 R2 and SCOM 2007 R2.
Cheers!