If so, just submit a TAC request and let them walk you through the configuration.
If this isn't an option, I have done a setup similar to what you are doing with ASAs on both ends and could probably get you some config examples. In my case, I setup two networks at the remote site, each with it's own subnet and VLAN. Then we routed both of them through the VPN tunnel to the main office, where they each connected to a corresponding network.
So using your addressing scheme, the first office would have:
192.168.5.0/24 routed to 192.168.0.0/24 10.1.105.0/24 routed to 10.1.100.0/24
You also need to decide if you want a split tunnel on the data network so computers at remote sites can access the net without going through the main office.
Then on the 891W, create VLANs for each network. Set the switchports to send voice traffic to the voice VLAN (The phones will automatically configure to the voice VLAN using CDP). Create DHCP for the voice network (Optional if there is only 1 or 2 phones, but I'd do it to be consistent across all sites).
Big caveat - I have done the above with an ASA5505 at the remote site. I don't know if an 891W can do all this. Again, TAC would be my first call tomorrow if I were in your shoes.
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