I had my bottom bracket break last summer, (cheap bike off fleabay, bracket broke inside a month). Rather than go through the hassle of getting it repaired locally and claiming blah blah I decided to replace it myself.
It was dead easy!
Bought a better quality 'sealed' bracket off the net for about £20 (I think it was from these guys
http://www.chainreactioncycles.com/S...archButton.y=0 but I wouldn't guarantee that) Prices for them can become extreme.
I needed a special tool to remove the old one, found the new one was a different type so needed a different tool to fit it grr.. got both cheap of fleabay again and in the end the job took maybe 30-60 minutes start to finish. Which is great considering I had never done it before and had no instructions.
Handy tools, big rubber mallet (or hammer and a bit of wood to protect against chips and dents) A stillson wrench or biiig adjustable spanner and a socket set (one of the special tools fit like a reversable socket to become a crank remover)
My advice, if you are at all practical, diy!