I had a great holiday in Cuzco and MP. I agree make sure you take your time to acclimatize a few nights in Cuzco is worth while and do not drink to much alcohol! I would recommend 2 nights at MP plus a day trip to the sacred valley is great.

As for the trek there are different lengths of the track you can do, different periods of time it can take and you can also carry your own gear or have it carried for you. It all depends on your fitness. But take your time and enjoy it.

It is a trip you will never forget