1.What do you do if a client has the same I.P. address as the service provider internal address range.
2.How do you differentiate the two networks what sort of config would you use.
EG Internal ip address range of our company 172.16.x.x and 192.168.x.x and 10.0.1x.x
Service provider internal I.P address 192.168.x.x and 10.0.x.x
What rules to you add to the routers at our company and what rules to you add to the router at the service provider.
2) Networks are defined by subnets. Essentially your subnet "mask" determines the network size. The IP address is broken down into two parts, the "network" and the "host" portion. In the case of a class C subnet you're looking at x.x.x.y where the "x's" are the network address and the "y" portion is used to define the host. This is configured on the hosts as well as the router(s). I'd recommend getting a good book on TCP/IP and reading it. It will clear this stuff up.
3) The address space you listed is defined under RFC 1918 as reserved private address space, meaning these networks will NOT be routed or used publically on the internet.
4) I'm not sure what you're referring to by "rules". You would add Network Address Translation (NAT) if you needed to translate IP address from one to another. These will vary based on your router / firewall and depending on EXACTLY what you're trying to do.
I've seen many ISPs use non-routeable/private IPs for their internal networks. As long as your router doesn't get confused sending data to the gateway assigned by your ISP, it should be fine. They always assign end nodes routeable address though.