Here's a couple quick thougths from a Missouri dear hunter who hunts Colorado elk every other year.
Sounds like your going with a guide, listen to everyhting he says as long as it makes sense but dont assume he is a better hunter then you, if you have a thought to try over the next ridge etc. give it a try, its your hunt.

Never drink the stream water and always have plenty of water with you, you dehydrate much faster at altitude. One liter a day is not enough sometimes.

Dont try calling (cow calling) unless you are hunting without a guide, let him do it. If you do call less is more.

Be in shape

Practice shooting to 300yds b4 you go. Practicing at 100 and knowing the holdover distance is not the same. That being said be prepared mentally to shoot a very big animal at 10yds, it can and does happen and it will rattle many expereinced deer hunters.

The open parks are pretty but you cant hunt cover to thick for elk, go in the dark timber and get them.

.270, cant go wrong with winchester failsafes, and in case you here otherwise, a .270 is plenty gun for elk, just make the shot. My son uses a 7mm-08 for elk and they die just fine

Last, its your first elk hunt, enjoy the hunt regardless of if you get an elk or not.
Good hunting...