BT1801 HG Router - Wireless set up???

[#1]

Apologies if I sound like a complete numpty, but I've not had a wireless router before.
My Plusnet account was activated on Thursday 7th Feb, and the aforementioned router arrived the next day. I decided to leave the set up until the weekend to give me more time, especially as my old Speedtouch 330 is still ticking over nicely.
I have noticed advice elsewhere that it is best to connect the router to the main linebox in order to get the best response. The existing modem connects to what was originally my separate dial-up line, but which was adapted by BT five years ago to become an offshoot from the main line at the point that it enters the house. (At the same time BT also replaced the line betweeen the house and the telegraph pole) I wonder if this makes the upstairs linebox the equivalent of the main linebox? 
The main linebox is downstairs in the hall, whilst the computer is upstairs in a back bedroom. I'm fairly sure that my two year old Dell Dimension 5150 desktop PC does not have a wireless card fitted, so what I would really like to know is what I need to buy - in terms of hardware - to set up a wireless connection between router and PC.
All advice gratefully received.
Thanks.
Spruance

[#2]

Spruance - why do you want to go wireless, apart from this allowing you to move the router to the main linebox? Wireless comes with its own set of problems, so don't go down that route unless you need to.
It sounds as though the upstairs linebox is not the main one - the main one should always be the one which connects to BT's incoming line. Even though you are on a secondary, that is not necessarily a bad thing. You've already said that your existing Speedtouch is fine - a good router should be better than a USB modem, so it is likely that your performance with the new router will either be equal to, or better than, what you had before.
The issue of moving routers to the master socket is generally so that the secondary's can be disconnected for testing, or where the wiring to the secondary's is "iffy"! Since BT did the work for you, it ought to be done properly with the correct cable. In cases where the secondary socket is well wired, and a short distance from the primary, it is quite likely that you will see no improvement at all. I'd suggest that before you do anything else, you temporarily move the PC to beside the master socket, and compare performance with what you get at the secondary. If there's no difference, save yourself any headaches of going wireless.

[#3]

Thanks for the info.
I don't especially want to go wireless, I just thought it might make the connection faster (??).
It would certainly be far more convenient to use the secondary socket, which was indeed installed by BT, and which is literally only a few feet from the PC.
There's currently nothing else in the house that would/could run off a wireless router so upstairs will do fine for me.
Thanks again.

[#4]

I'd just like to round this topic off with a thankyou to Richard at Plusnet Support for talking me through a glitch on the router set up this afternoon.
It's so refreshing to know that the people on the other end of the line really know their stuff. 
Spruance