Wireless Over Distance

I have two buildings on my property, about 100 feet apart. One houses my office which has an intel mac on dsl through a modem, airport then an ethernet switch. In the other building I have a G4 I'd like to connect to the wireless network but the distance seems to great. It recognises the airport network, can connect but loading a web page takes an age.

Would upgrading the airport to airport extreme help? Would this need an airport extreme card for the G4 or would the existing airport card work?

Lastly, is there an amplifier for the airport signal that would allow a better signal and is there any health issue with these similar to that for mobile phone signals?

You are going to need an antenna.
http://www.quickertek.com/PNP.php

I do not there there is any more of a health issue then using the airport with out an antenna as its the same frequency. If there was a health issue, you would have to be exposed to the signal for a very long time, at very close range.