Many thanks to everyone who replied. I got a really
good scripting example for how to set something up
off list.

I'm going to use sudo,
http://www.courtesan.com/sudo/intro.html, to give my
user login access to nice, renice. Then create a shell
script with the command I need to launch mpg123 with
a higher priority. I'll then execute the script.

<just a long rant>
I'm a field service engineer, for a company based in
Israel, but I work out of Santa Ana, Ca. (I just moved
from Phoenix a month ago.) We use Solaris 7 and SunOS
4.1.3, (very old), as well as HPUX, and no one here
could answer the question. Most are user level, it seems.
Which only reminds me, again, of the many hats a Linux
user has to wear. My guess would be that within a very
short time, simply stating that you use and maintain
a Linux box will be held in higher regard than most
available certifications.
I got the job based on my knowledge of the unix environment,
limited as it is, and I have never taken any courses for
this OS. I have been struggling with Linux for about
four years, though, and have loved every minute of it.
</just a long rant>
-JR