Hi,
my ex-girlfriend guided that trek very often, like 10 times in two years, and it is a very very hard trek for someone not used to that kind of activities. Also the weather can have some impact on your motivation, as rain and cold are common. But if you are in good shape and do it the right way, you should be able to do it.
It is important not to expect it to be a walk in the park... it's not just a trek, is an ascencion, just not a technical one.
If you can read french or want to see nice pictures (not only of africa) i suggest you look at karavaniers.com website. It's an adventure travel company in Québec that offers some amazing trips and their website has a lot of information. In fact, i think it's the nicest website I have ever seen! The link to the kili trip is :http://karavaniers.com/voyages/repertoire/kilimanjaro/index.html
What they do is climb mount meru to acclimatise, and then do the kili. Afterwards, they do a safari in the serengeti.
they do the trip in 16 to 20 days depending if you do the safari or not. The acclimatisation climb of the Meru (wich gives you amazing views of the kili) makes the Kili a lot safer, and also gives you better chances to make the summit. Hope this helps!