Title says it all really... How do I contact an admin or speak to someone about changing my username, I must have mixed the fields up somehow and can't find how to do it.
As for the OP's question, if you have a Garmin Connect account, try going there in the personal settings and changing the display name.
I used to have separate display ID's for Garmin Connect and these forums. But awhile back they did something that ties my forum alias to whatever my Garmin Connect account is (which I don't like). So maybe that will work for you.