DRS is a bit of a lottery as it depends on what car you're driving - some have a first green LED light that activates when DRS can be used and a second when it is open. But somebody at CM fudged this as, for some cars, you only get the first green light and have to use your mirrors to check whether it's open (which is how I check).
I guess there might be a custom HUD or something out there that does this though, but I don't know.
I'd like the hud too, actually I would be happy already if I could only see the gear I'm in. It looks like it's not possible though. The best I could do was messing with the vertical offset until the gears are visible, but it's kinda crappy because this makes the car higher than my steering wheel.