Depending on conditions, the top part is often iced up so that you need to be comfortable climbing on mixed terrain in crampons, even in mid summer. The rock is very bad. You should practice scrambling on bad rock and talus in exposed places to make sure you have the confidence and balance. Some guides will not take clients with no climbing expereince, since the guide is relying on you, too. However, when Fred and I climbed it in 1985, there were plenty of people being guided who very obviously had little experience and many who where unguided who had no business being there. The day we arrived at the hut, a person had to be helicoptered out, because he was severely injured by rockfall. There are an average of 40 accidents each year and 12 people per year die on the Matterhorn.
It is very expensive - the <a href="http://www2.zermatt.ch/alpincenter/">local guide's office </a> charges about 1200 CHF per person. They will not guide you unless you have done one other climb with one of their guides. So you are probably in it for at least 3000 CHF each. Guides from outside Zermatt charge about the same and usually want to be sure you know what you are doing.
The more experience you have, the better. You will also enjoy it much more.