Wobbly bottom bracket on Radford, need guidance to replace I have an aluminium frame Raleigh bike that's been stuck at the back of my garage for a few years now. It has a wobbly bottom crank. I assume the bearings have gone, but A; I don't have the tool to get the crank out, and B; I don't even know if the crank can be replaced.
It has square things that the pedal stems attach to each side, and after I managed to force the pedal shafts off the crank, there was a thin nut (lock nut?) which I removed from the protruding thread. I don't have a picture currently, but the right side(where the thin nut was) looks like the left side of this picture;

which is a Tredz.co.uk Raleigh crank.
So how do I find out which crank I need and what tool I need to remove the old one? Also, do I need any extra tools to install the new one?
I'd love to get the bike working again, and the cranks seem to be pretty cheap.
Edit:
Here are the photos:


Update:
Thanks to you guys I could move forward with a better understanding of what I needed to do. For clarity, here are some better pics of the bike and the removed BB:
(click for original size)





I mistakenly thought it was a Raleigh, but that was my other bike. This one is a Radford. The new BB I bought looks a lot like the one I posted first actually.
Thanks for the help Guys.
What you have in the picture is a cartridge-style bottom bracket which contains the bottom bracket bearings. What you called the 'pedal stems' are the cranks.

Cranks should be removed from the square tapers on the bracket shaft with a special crank puller tool such as the Park Tool CWP-7. If you forced the cranks off by other means you have possibly damaged them. If re-installed on a bottom bracket they may keep working loose.

The bottom bracket is removed using a bottom bracket tool such as the Park Tool BBT-22 that fits into the splines in the cartridge body.