You can't put it into PC Suite mode without the screen working AFAIK.

What you can do is use the Meego intrd from a Linux computer (you can use a live CD or USB if you don't have an install availiable) as described here, which will allow you to put it into USB storage mode, in this mode you can copy all the data off, including the contacts, although the contacts are stored in a sqlite database which unless you are planning to transfer to another N900 isn't quite straighfoward to move to another phone though it should be possible to convert it to vCard format which is somewhat compatible with other phones.