Couldn't wait so I tried.
The service code doesn't allow me to remote in... Unless the username is something special. Tried the code, admin, administrator... I give up.
I'll bug my service rep for it, he emailed.me.the service pin without me even asking for it so I doubt he'd mind.
It's dumb that hp does this anyways... They gave the code for the 3/5xx out themselves for head warranty... I get they don't want people to mess with settings and break their printer... But just throw up a warning or something.