Being that I was born and rasied at altitude - and recently moved to the area, the main thing I can say is:
Hills at altitude are MUCH harde then hills at sea level. The course itself actually isn't too bad, though there is one steep hill (and one minor one) that you (on the 8k course) go up twice. The main thing about adjusting to altitude is running by feel - not by your watch. Like Jack Daniels said: at altitude, you learn how to hurt. Basically, your lungs will burn A LOT sooner then usual - though you just deal with it, it doesn't get worse, and it doesn't get better, it's simply there - so you learn to deal with the pain until you're just used to it and don't notice it as much.
I would agree with the previous posters - if you can't get out here early, just continue to trail on rough terrain (HILLS), though the earlier you get out here - the more time you'll have to adjust.
I've been here for three weeks and I don't notice the altitude on my daily runs anymore (at 5,000+ ft; if I go higher - to 7,000+ THEN i notice), but if I run hard (intervarls, tempos etc), I notice a lot sooner.
Depending on your altitude now, you can get an idea of what you could run for any distance up here - there are websites that convert for you, but basically at the Buffalo Ranch, it's about 9-10 seconds slower then sea-level times. (example - if you run a 19min xc 5k at sea-level, that's worth about a 19:30+ 5k up here).