Ok, I know exactly what you are doing
First and foremost, Peru is by my account, the greatest place I have ever visited. You will be completely and utterly shocked, fascinated, as well as immersed with a unique culture.
Make sure you spend at least 2, even better 3, days in Cusco. Most travel agents are smart enough to do this for you. The altitude is high. I believe 11k for Cusco.
Drink the Coca tea. They will hand it to you constantly. While in Cusco walking the streets, chew it like tobacco.
Reserve your energy as much as you can, when you reach Machu Pichu, you will be told that you can climb Temple del Sol. Be careful with this, it is a third world country and parts of this hike are tough, a bit frightful, however very worth it. Here is a shot from there:
Get your camera ready for the Gateway to the Sun. If you can, bring a tripod. Don't worry with the guides at that point IMO, you can walk the remainder yourself, I wish I would have had the camera equipment I have now, then. You can always buy another tour guide on site at Machu Pichu.
They will send you hiking early so that you can see the sun rise over Machu Pichu (Gateway to the Sun). With any luck, the sun will be out. But even if it isn't, it is worth every shot you will take.
Not a great shot, I am tempted to go back
Feel free to peruse my gallery (below). I didn't make Peru due to turbulence over US oil lines, however I made Brazil, Buenos Aires. South America is amzing and Peru is the staple of it all. The people are wonderful. People will tell you Lima is scary, but it really isn't. Be careful, use common sense, always pay off the door guys at your hotels (especially in Lima), they will see to it that no cabs rip you off, if you need something, they get it....I would suggest giving the door guys $20 a pop right when you walk in the door. (I mean, if there are only a couple, etc...) Otherwise, give some cash to a few of them.....It will pay off. That includes Cusco, however Cusco is very removed Lima's harder, faster pace.
http://www.gomidgetarmy.com/gallery/album42