Please help with wireless signal

i have always been a windows XP kinda guy i guess and have been using a dell laptop for years with 802.11 built in. my family and i have a lot of property and my little "workshop" is a bit aways from the house. my laptop never had a problem reaching where i was. i now do not have the portability because i purchased an imac G5 desktop 17" computer.

i though the G5 would look more professional in the shop if i ever have a customer come by. so here's my problem... it has airport extreme 3.5 built in and it is the older model w/out built in cam and all but i have the external isight cam, but anyways, the airport will not connect to the house... and i do not want to spend all the money for a booster.

What i have seen is the 802.11 usb adapter on ebay as well as on a few sites i.e.: afterthemac and macwireless... so if anyone can answer...

Q. what is the best adapter to buy and will it give me the same performance?

Q. if anyone has used this, can you give me a specific link to the one that is the best that will boost my range?

Q. am i going to waste my money thinking this will give me laptop performance and should i sell the G5 and go back to a laptop...?

please guys, i love the way this thing looks in the office and really want to keep it but i need it to connect reliably so i can get prices, parts, communicate with vendors, etc... to keep my business going. thanks for everyones help in advance.