Watchguard:Mobile User VPN questions

I wonder is there any way to setup a Mobile User VPN to connect the firewall without changing any network setting(windows ip setting) of the mobile user (like IP addresses, subnet, gateway, etc...) for example:

1) Office A (watchguard firewall VPN server setup) internal ip: 192.168.1.x

2) client B a mobile user; internal ip is also: 192.168.1.x

According to what I heard from a consultant, he told me that in order for client B to connect the Office A with using Mobile User VPN, I will have
to change the ip setting of the Client B to 192.168.2.x or whatever ip that is not under 192.168.1.x.

Is that statement true?

If yes, it will be an issue when Client B in a hotel or other places where the site ips is 192.168.1.x because I don't think I may able to change the ip setting of a hotel or other places.

If no, or I just need to setup a profile in the VPN server(firewall), and setup the firewall client software on the mobile user machine. and every IP setting will be taken care by the firewall? Thus I don't need to worry about the Office and the Client both have same the internal ip range(in the example above: 192.168.1.x)

P.S.: I am looking into watchguard firebox X series.