For yahoo- there is no way that you can run the latest yahoo messenger in ubuntu. I have heard that older yahoo messengers used to run in wine. But its not gonna work. The best instant messenger is the empathy which come with ubuntu (which doesnt support yahoo conference). You can do yahoo conference in pidgin but without voice.

For video chat- use skype. I think it works pretty good.

For drivers of  the printer: there might be generic drivers you can get. I don't have any printers, so cant give you much info regarding that. But a quick google gave me this link which says that all HP printers work pretty well in ubuntu.

ubuntu is awesome, but it gives pain in the neck once in a while for sure. If you have any other ques, let me know or IM me.