1) Especially check out the -k, -h, -s and -c options of "du".
2) is more tricky, since the services can have files in any location on your disk (ie config files in /etc, programs in /sbin, ...). Why do you need this information exactly?
The only way I can think of is an approach like this:
* first get your package manager to list all files in the package of the service you're investigating.
* Then write a little script or something to get the file sizes and to display the total size.
More likely, though, it's not the services that are taking up all your disk space. Rather, it'll be all the software packages and multimedia files (pictures, movies, music) you put on the disk...