cisco ASA or Watchguard XTM 515 and NVG510 issue

I am setting up a small business network.  They need to do a vpn tunnel to their main branch and another off site location.  The main branch has a watchguard with a static IP and an internal LAN.  I use a lot of VLANs on that main system.   The one I'm setting up requires me to use U-Verse.  Well I've tried several of the fixes and to no avail.  

This U-Verse has 5 static IPs set, with the IP like xx.xx.xx.10 to xx.xx.xx.14 with xx.xx.xx.15 being the NVG510/Gateway.

The internal scheme for the Main system which I will be VPN tunneling to is 10.0.xx.xx, with a static IP.  I can set the router to whatever works.  So my question is or frustration, the Cisco router freezes when I try to change it's internal IP to 192.168.2.1 vs 192.168.1.1.  Since the main router is 192.168.1.254/29 (plus the static IPs).  What do I do to get this Cisco to work. If it doesn't work then will a Watchguard XTM to Watchguard XTM be easier to to tunnel between?  If so I can do that as I have a few lying around.

The other site uses a Cisco as well.  Both the Main site and the other site are using other ISPs.   This site is UVerse that I am setting up for a client.   

Any help or suggestions would be appreciated.

Also, I've read a bit but none of the typical soiutions are not working.