Tough Mudder are you in shape enough?!

In an attempt to somehow regain the glory of my youth, I signed up to drive three hours (one-way), run eight miles through a military style obstacle course annnnnnnndd jump into a freezing lake on the top of a mountian. Perhaps I am merely recapturing the stupidity of youth but hey, there are free tattoos and beer to all finishers! Irregardless, I am excited about the race. It looks like a lot of fun and I think that there is only one thing that may impede my testosterone fueled age-reversal experiment....I haven't really been training. Don't get me wrong, I went and ran 8.37 miles up a hill last Saturday and made it just fine....well, it hurt a little.....ok, ok it hurt A LOT. But the point is that I did it. Unfortunately, the race will take place well above sea level. Try 6500-8500 feet above my current 50 feet above sea level. My obvious out-of-shapeness has even begun to worry my wife. She made the comment that she didn't think I was ready to go. Fifteen minutes later I lay exhausted and sweaty on the couch after having performed many feats of physical strength to prove my readiness. (That sounded way better than it should have, I should of said "fifteen minutes later I lay exhausted and sweaty on the couch because I had been thumping my chest and acting like an ass to prove my worthiness to go die on a mountain in the Sierra Nevada's.) Anywho, I'm pumped and I may not be in peak physical shape, but hey, if I waited till then I'd never go.