Can anyone tell me what the specific settings are needed on the WRT54G with DD-WRT for UMA to work on my 8320?

Mine works without any changes at all - running v2.3 SP2 on a wrt54g 4.0 at home, it kicked right in the first time I used it. Basic WEP security, b/g mixed mode - nothing configured out of the ordinary, no QoS settings touched.

Mine works ...sort of but I get dropped calls and lose my connection. Also sometimes I only get two bars even standing next to the router!

See the other threads about this which will recommend changing channels and stuff like that - I don't think your problem is DD-WRT specific (at this point), debug all the more common issues first. You didn't say but are you running the latest stable DD-WRT release?

EDIT: ps update your profile so we know what device you're using.

I've tried all the recomendations here and no luck so far. I'll have to go home and check what release I have.

Yeah I think that's first and foremost - I'll take a look at my webUI config when I get home (if I remember ) to see if I have any settings that might matter - I didn't explicitly touch it though, I haven't changed it in a year maybe.

A lot of people here are advocating setting up QOS and WMM. Last night I looked at it and I wasn't sure what to use for some of the required parameters (bandwidth, etc.)

That recommendation is 100% valid - personally I don't need it, I'm the only person on my wifi (usually) and am aware of my network traffic. Prioritization and QoS shaping isn't needed in my home, but obviously for many folks it is necessary.