Hi. The bottom bracket cones on my trusty 1984 Peugeot P-something have worn out. I'm thinking it might be time to replace it with a sealed BB. Thing is, I've never actually seen one -- all my bikes are pretty old. So, tell me: what do I need, both in parts and in technique?

The shell is, as near as I could measure it with the cups on, 72mm wide (maybe 73?), and the threading is English. The current spindle is (I think) 121mm. Is this a good choice? What else will I need? Thanks!