Nope. The WGR614 is a "wireless router" or an ethernet router with a WAP (wireless access point) in the same package. A "range extender" is a marketting term and is something completely different.
Sure. See:
The 2nd WGR614 router get configured with: 1. A different IP address from the first WGR614. If the main WGR614 uses 192.168.1.1, then the 2nd one should be 192.168.1.2 in the same Class C IP block. 2. Turn OFF the DHCP server. Only one DHCP server on the LAN at a time. 3. Nothing gets plugged into the WAN port. Connect a crossover ethernet cable between one of the LAN ports on the main WGR614 and one of the LAN ports on the 2nd WGR614. This converts it from a router to a WAP. 4. Use the same SSID on both wireless boxes. However, use different non-overlapping channels (1, 6, 11) to prevent mutual interference.
Mostly wrong. Nice try. See above instructions.