1. Sorry, nothing to say about wifi.
2. The easiest way: YaST -> Software -> Install and Remove Software -> Filter:'Search'
If the software you are looking for is not present, you may need to add more installation sources (see: sticky thread about YaST update sources). If you still do not find what you are looking for, try
http://linux01.gwdg.de/apt4rpm/home.html or compile from source.
3. On your login window you should have the choice to pick a windowmanager (if it is installed).