LAN network

I want to setup LAN network for a small orginaization having 8 PC + 1 Server + 1 Linksys Modum + Linksys Rang Extacher.

how I can do?

I creat in a way

1- Modum will provide Internet for the user
2- Extanger will extend the internet conaction
3- Server wireless also will provide workstation

the problems
1- Alwys there is internet disconect from Far distance users but they are near extenger.
2- some users can not access public folder in the server.shoud put network admin password
3- Ip conflect in the user site and the server