Need help with wireless connections WRT300n and WRT54G

I bought a WRT300N to replace my WRT54G and I installed 3rd part firmware on my WRT54G (www.thibor.co.uk ), which provides a wide range of new options regarding WRT54G configurations!
How can I boost the signal to 100mW? It's automaticaly changed when I install the 3rd part firmaware?

Now another set of questions:

1) Using my WRT300N to access Internet, can I use (the old) WRT54G as AP or Repeater in order to cover unconvered areas of my house? If make sence should I install 7dbi HGA on the WRT54G? What sould be the configuration of both devices?

2) In order to my wrt54G work as AP or Repeater, can I make it wireless or should be connect with a Ethernet cable to the wrt300n?

3) How can I safetly access my WRT300N from the office, just to check if anybody at home is accessing Internet? I guess I need the Router IP plus the port number, but where can I found the IP of my router? Is the Local IP Address? Isn't this IP the same for all the routers? Can I change it? What should be the rules for the new IP? What's the subnet mask for?

4) Does it make any sence to use WRT300N to access Internet and wrt54g as a dedicated firewall?

5) I'll try to find if available a Linksys-N NIC to install in my PC to access wrt300n, instead of the ethernet cable connected to the 10/100 PCI NIC, in order to take full advantates of the Wireless-N solution. How can I check the speed between the wrt300n and the Linksys-N NIC? Or in other words, how can I check the speed between to wireless devices? (Router/PC, Router/AP, Router/other wireless devices, etc)

6) Does WRT54g or WRT300n inclued a tool to scan/detect/track other wireless networks on the neighborhood?

7) How can I measure the strength of the wireless signal that is been sent from the antennas?

thanks in advance
Ayala
Lisbon, Portugal