We just did a two week tour with Gate 1 in January, it was wonderful and we did Abu Simbel, which was great.
Cost including airfare was $3500 pp in top hotels. Tour guide was fantastic. What did your tour cost.
1) We didn't purchase any Egyptian money, but did bring about $500 in US, which included lots of ones and fives for tips. Also, of the 500, much of that was for the tips of the guide, the two river cruise ships (2 three day cruises) and other tips for staff at hotels.
2) If you need local currency, like we had to pay in Egyptian Pounds a couple of times, we got help from fellow travelers that used an ATM. Cash was needed to go inside the Great Pyramid of Giza and an additional entry into tombs at Valley of the Kings. It wasn't a lot.
3) It will be warmer in March and Jan, but we were surprised by how chilly it was at night, in the early morning and evening. The cruise ships and one hotel in Aswan were top ships, but didn't have heat, and we had to bundle up. Be sure you take a good jacket, I took my nice leather jacket. Still, I wished that I had taken a sweater for the chill.
4) Do not drink anything, water, beer, wine, sodas, unless you open the bottle or watch someone open it. Never drink tap water and even wash you toothbrush in bottled water. It will be hot during the day and you will need lots of bottled water. Our tour guide and bus driver provided as will as the hotels and cruise ships. Also, never eat street food. Best to only eat in top restaurants in the equivalent of four or five star hotels.
Enjoy, it is a wonderful experience.