Im still new at technomancing.

I've hacked into the johnsons commlink and I've got a courier sprite with stealth.

I wanna find out as much as I can about him? What kinda questions can I be asking and what should I look for? I need to know about his friends, contacts, buisiness... As much as a runner would want to know about somebody...

How do I get my requests across? I've got admin access on his commlink.

You can access everything M. Johnson has on his commlink, so it depends on what he actually has on his commlink.

If he's a professional Mr Johnson, the commlink probably won't really be his own commlink and you'll only get whatever he put there, which can be false information.
If he's a regular corporate employee, you'll get access to all his professional and private life, though secure professional messages/documents might be stored in a more secure server and you'll only get a link to these files. But even then, I'm not sure a regular corporate employee would risk getting his commlink hacked when meeting professional criminals (especially if he knows that one of them is a Matrix specialist) so he might have turned it off (at least the wireless part) for the meet.

The guy is more of a side plot.

High level guy in a low level gang. I've been watching him play on his commlink for awhile now and I want everything.. Is there like a steal everything command I can give a sprite?

Well, you've got admin access on the commlink, which means that you can do everything he can, and you do it exactly as a legitimate user would.
So you can probably dump the content of the whole commlink to some storage you have access to. No need for anything fancy to do this, an Edit program should be enough.

You may also want to check out the Cookie power of Sleuth and Courier sprites. Detecting the cookie is not an extended test and requires 4 hits on Matrix Perception. If you have Admin access swap his Analyze programs for rating 1 Analyze Programs or a Rating 6 with the program option "Limitation: Will only act against people" so it doesnt even try to look for your cookies. The GM might also allow you to have the program not identify itself any differently so the mark would be none the wiser...

Don't forget to cover your tracks and edit any system logs after you're done.