Newbee sound problem etc

After tweaking debian 8 to have a gnome2 look, i am very happy after installing Ubutu MATE on an other machine. Though i have two problems which have to be solved:

  • Major problem is that i don’t have sound. The pc is an old asus a3a. Though the system software seems to work fine - indicating i have input and i have looked at input/output parameters. Any suggestions?
  • Minor (linux) problem. I want to change some icons by choosing from the default set, but where the hack is it? If i click the preferences of an existing (default) icon, and want to change it, it does not show the path. I have the default Ubuntu MATE 17 installed.

Thanks in advance