[dba-Tech] Kill a Workgroup and Replace it with a Domain

Way back when, I set up my home network, back when I knew even less than I
do now, which is almost nothing. When it asked if I wanted to set up a
domain, I assumed that it meant an internet domain, which I didn't have, so
I chose Workgroup.
I would now like to change this, and ultimately arrive at an Active
Directory solution, replete with roaming profiles, so that no matter which
box I am on, I see the same Outlook files, the same shortcuts, etc. 
In short, how do I get from here to there? Should I just remove everyone
from the workgroup, then destroy the workgroup, then create a domain, then
add the boxes to the domain, and finally add the users?
If not this, then what? I have tried a few googles and got nowhere useful.
One more thing. I have purchased a wireless router, but not yet set it up.
The intended purpose of this box is to allow immediate access to my network
to several selected people only: clients and colleagues. I want a client to
be able to visit, turn on her notebook and immediately have access to my
network -- not complete unfettered access, of course, but access to areas of
interest to her. The list of clients/colleagues is small; less than 10 --
and the only way they will ever access the network is by bringing their
notebooks here.
In addition to the clients/colleagues, there are 4 others to whom I want to
give roaming profile abilities, so they can log in to any available box and
see their stuff and not see the stuff to which they have no access.
Any advice or URLs leading to a solution will be much appreciated.
A.