Need help setting up XBox Live wirelessly.

I've been putting it off for ages, but I got paid today so I figured it's about time to set up Live. I tried it once before (Not live just setting up a wireless network) and I got so annoyed I ended up leaving it.

My Broadband computer is in the living room connected to the family PC. My 360 is in my room upstairs, with my personal PC...Now I'm guessing I need to set up router... But I found this on Amzon:

http://www.amazon.co.uk/Game-Point-Wireless-Gaming-Adapter/dp/B000FYKVM8/ref=sr_1_4/203-1223983-8256709?ie=UTF8&s=videogames&qid=1174650819&sr=1-4

Although I'm setting it up for 360, I also have a DS and PSP, so if I can set it up to play them online too that'll be great. However, I just want it to be fairly easy to set up, so if I brought that Game Point thing above, what would I have to do to set it up? Can anyone help me out here?

I tried that once already, and it didn't work. Oh, one point I forgot, theres a stair lift in my house for my grandparents... I don't know if that will cause problems...

Can anyone recommend a router thats easy to set up?

i have a netgear wireless router and its pretty easy... they all are really. all you do is basically turn off you computer and 360. unplug your internet from your computer and you may want to turn off or unplug your internet too. Then just plug the cord from your internet connection to your router, then your router to your PC (they give you an extra cord usually). then turn on your internet and your computer.

next you have to insert the CD and just follow the instructions on there. dont turn on the router until they prompt you to (leave it unplugged). do not setup security unless you know what to do because sometimes it can cause problems with stuff connecting to it. Once thats all done everything else should work fine. the 360 will automatically connect if you have the wireless adapter.