Wireless security question...

 Hi,
 
We're having an in-house discussion regarding the risk
related to wireless security.
 
The mobile users would like to be able to use the wireless
technology within their laptops to access the office while
they are away. Right now we don't allow wireless access
points.
 
The questions we have are:
 
1- Can a wireless router (installed in their home-office) be
hacked into AND can this hacker take control of the wireless
laptop. If so I would need some detail on how we can prevent
that (besides WEP). Let's assume for the sake of discussion
that there is no WEP encryption on the router. 
 
 
2- How easy is it to access the laptop once you're into the
router? Is it child splay or do we need a specialist?
 
 
3- If the laptop's wireless router is secured with WEP and
connected to the office via VPN can it be EASILY hacked
into? The VPN connection gives them little access to the
network, barely what they need to work. Will the intruder
have access to our network?
 
 
4- How secure is my sales rep. running around hotels with
his laptop? 
 
 
 
We are trying to assess the risk...should we, should we not
allow wireless for the mobile workforce.
 
 
 
Thanks!
 
Marty