Well...Let's see here - on a normal day (non-game day) it takes about an hour & a half or so to get from C-Springs to Denver...
On Game days, I don't know...It's that last little bit of a drive through Denver that slows you down...as kick off nears, the traffic tends to get worse...
If you want to tailgate for a bit first, I would leave no later than 9am - get up here around 10 or so, and come find the bus - http://www.orangeforceone.com
to meet up with me & a few other maners. We'll be in Lot C, just south of the stadium, west of the players parking lot...RV spot 31...If you can't find us, you can ask any of the event staff (blue or yellow jackets/polos) where the lot is & they should point you in the right direction.
If you're parking anywhere near the stadium, expect to pay upwards of 30-40 dollars...There are a few places you can park nearby for cheaper, but a bit longer of a walk.
As far as how long it takes to get back...Just depends...How long you plan on staying around the stadium after the game. If you're one of those "leave early to beat traffic" type, you'll probably end up sitting in traffic for quite a while...If you stick around for a while till the lot clears out, then you can expect the normal hour to hour & a half drive to the Springs.
I think/hope I covered everything...if not, let me know.