Hi,
I suggest you use a guide. He will provide you with a lot of information that you would otherwise have difficulties acquiring. Further, some of the paths on the mountain are very hard to follow which means that, without a guide, you may be limited to the 'most used paths', and with 7-8 days on the mountain you have the time to visit some of the more remote parts of the mountain.
If you are in good shape, I would recommend trying the 'Peak Circuit' which is a long day of hiking passing one great scenery after another, while hiking around the top of the mountain. It may be possible for you to find your way without a guide, but I (and I do have some experience) would not have been comfortable doing that.
For inspiration, visit my facebook album:
https://www.facebook.com/media/set/?set=a.10202514620006771.1073741826.1233495052&type=1&l=252eb6cd79
I was also guided by John Mukuruma and found that he was really good. As Christopher writes, his facebook is:
https://www.facebook.com/johnmukuruma.ndichu
Regards,
Dan