I did it three years ago, in May, with GAP (
http://www.gap.ca). I was very happy with them and they are competent, at least for Peru tours. I also did a Amazon tour for a few days, along with Cuzco before the Mauchu Picchu tour.
Don't take the "short" tour (1 night) as it doesn't go on the historical pathway. Take the "long" tour, which is 4 days 3 nights (more or less).
It was luxurious and a trip of a lifetime. They fed you and carried group gear and 5 kilos of personal gear. You carry what you need for the day in a daypack (raingear, lunch, camera, water). They provide food and tents. Bring a sleeping bag and pad. Hiking poles must have rubber tips to not wear out the pathway.
We started at Piskachuchu (Km 82). The first night was below Dead Woman Pass, 4200m, the high point of the trip, which we reached the second day. I got a little altitude sickness before reaching the top of the pass, but I was ok the rest of the trip. The second night we stayed at Paqaymayo, and last dnight at Winaywayna. Terrific forts and ruins along the way. The final morning we got up early, before sunrise, and reached the Gate of the Sun with the classic view of Mauchu Picchu and saw the sun rise on the place. Very impressive.
The ruins are crowded with people, but when you first get there in the morning it's not so bad. Enjoy and ask follow-up questions if you wish.