I have been there a number of times for work and I would say fall and spring are the best times. I would avoid July and August due to the heat. Upper Egypt is going to be like 10 degrees warmer than Cairo so June and September are going to be pretty hot there. Look up Muslim holidays and make sure you're not going during Ramadan.
You are going to want someone that is able to speak Arabic at all of the tourist sites and traffic is crazy there sometimes so it may be better to book everything thru an agency so everything is lined up. I clicked the link of the guy and he is thru Kanoo travel. I don't know the guy but the company I was with used Kanoo to book our travel.
On the number of days, I think it depends on if you will be doing a nile cruise and how many days. There are a number of options and I would look at viator to narrow down some options on number of nights. We never did one, but lots of people I worked with over there did them and said they were great.
While I was there we visited all around Cairo, went to the North Coast, Red Sea, and did Luxor. We never made it to Aswan. I think Egypt has some under rated or not very advertised beaches but you would probably only be there for the history sites. The Red Sea is know for world class diving, but I only snorkeled there.
As poster above noted, there is a lot of aggressive selling at the tourist sites. When I first went there it was 15 to 1 Egyptian pound to dollar and when I last went it was 30 to 1. I think now it is 45 to 1. A lot of inflation and people hurting there. A lot of the guides probably get kickbacks at places so a lot of them bringing you to their favorite spots even if you asked to go somewhere else.
I don't have much insight on costs as I was traveling for business most of the time. I know the airfare seemed like the most expensive part. Lodging and food were relatively cheap. I believe you can still bring in a bottle of alcohol and you are able to use your passport to get something at duty free if you need alcohol while you are there. I would avoid the Egyptian wine. Gave me a headache as I was drinking it.
I would say my musts in Cairo would be the pyramids, sphinx, Saqqara pyramids and the khan al kalili(market). There is the citadel, Coptic Cairo, and the museums as well.
In Luxor, we did the temple, Karnak, the queens temple on the other side of river - not going to try and spell it, and the valley of the kings. Everything there was pretty packed with people. A popular thing in Luxor is to do a hot air ballon ride but I was not brave enough. Working in Egypt everyone joked that you should never lean on a railing. I wasn't about to trust a hot air balloon. I thought Karnak was the most impressive site there.
If you choose to go to Aswan, you can also do Abu Simbel. A few folks that I knew that made it there said it was really neat.
That's probably just a starting point.
