Some simple basics. To get your gateway/router address, Start > Run > type: cmd. At the prompt type: ipconfig and then Enter. Note the gateway address (eg 192.168.1.1).
To ping, same procedure but type: ping 192.168 etc and Enter. Wait for the pings to finish. It gives the min, max and average ping times. The ping time is the time it takes to send and receive a small packet of data.
To your router, the time should be a few milliseconds. Try pinging 209.85.225.104 which will test the ping to Google. Depends on where you are but should be significantly less than 100milliseconds.
You can get to your router settings by putting the gateway address directly in your browser address bar.
The symptoms you've quoted could be a hardware problem. If someone is stealing your bandwidth by wireless I would think your Ethernet connection would also be affected. As you indicated more than one laptop is involved, it's unlikely to be a problem there. I assume that you would have tried the laptops close to the router.
Try turning off power at the router, wait 10 seconds and power up again.