When I went it was one part of a longer holiday encompassing a 17 day safari through Zimbabwe and Botswana, the week climbing Kilamanjaro and finished with a weeks scuba diving in Zanzibar.
Anyway it was organised through Travel Bag in Alton, Hampshire, we went up what they call the Coca Cola route, it has bunk houses and a large communal areas for eating at about 4 diferent altitiudes, the last being a few hundred metres (in height) from the summit they wake you at midnight with the view that you will be on the summit for the sun rise.
All your kit is carried by sherpas and you just carry a day sack.
Even doing this way a lot of people don't make it usually due to altitude sickness, I can only imagine that carrying all of gear only makes it even harder.
You will start in shorts and t-shirt in a tropical forest raising through different levels until reaching what is classed as Artic Dessert, where you will need some seriously warm gear.
Make sure to keep some proper bottled water for the last night (even if you have to carry it yourself) as you will not be able to get fresh water on the last night only filtered sterilised water from a stream that is just about undrinkable and a few mars bars or similar for energy.
The biggest problem is the lack of oxygen if you excert yourself near the summit and get out of breath it is very difficult to recover and that is what makes it so difficult.
Would I do it again?
In a heartbeat.
Hope that helps.