Yvette,
There are a lot of devices to choose from so if you can get to the shop yourself especially if you live near a big John Lewis shop then go have a look and a hold of the various things on offer, but dont buy anything straightaway.
Darth already mentioned using a ethernet connection to your old computer from the wireless router, this is the same type of cable that connects you now. I just checked with Mr Sunshine and he said that if you are using Windows XP then there may be connection issues with a new N class router, so when you phone your isp to ask for a wireless router it is worth checking with them first.
Isps often charge for the new wireless router and the install but there might be some wiggle room for the sales person especially if you are near contract renewal point.
We use Virgin Media and for the initial install a man came out to set everything up eg tv and broadband, but since then if we needed a new router they just send one out.

I leave it to mr Sunshine to set up because he likes a bit of new tech so I have not set one up myself but I have seen the instruction sheet is straight forward. If you get stuck you can use your old computer to ask questions here because you will be able to connect using the cable eg its just plug in and play.
In regards to netbook, laptop, or tablet it depends on allsorts of factors eg if you use a laptop it will have to be on a hard surface eg a tea tray and not the bed or it risks over heating and causing internal damage. If you can have a try at typing using the on screen keyboard on a tablet and see how it feels to you, for me the lack of feedback because there are no actual keys make it difficult to type anything of length. Tablets are really good for reading in bed especially when reading what would have been a thick novel, you would need to price in a case because they make it easier to hold and usually come with a stand.
For me the main drawback of my Sony S tablet is that I had a habit of reading a book for a while then checking out Ouch Too before going to bed, and if I wanted to reply to something there and then I would have to get out of bed and go put the laptop on.
