- What tools do I need to remove the bracket?
There's a plastic cap on the sides of the crank that you can pop off or unscrew, and inside there will be a Hex socket of about 6~8 mm , or a 6 sided nut to remove with a suitable socket. A spanner will not work.
Then you need a crank puller to remove the crank arms from each side of the BB axle. This tool threads into the crank, and exerts pressure on the end of the axle to lever the crank off. These threads are normal right-hand threads. And you will need a large 200~300mm spanner to turn the crank puller.
Note that if your BB is not a visible square when you've removed the bolts/nuts then the crank puller will need to suit the "octalink" or "ISIS" interface.
Now with the cranks off you'll probably see two different ends. The left side of the bike will have a lockring and someting like this:
So you ideally use a hook spanner
along with another spanner like this:
You can use a slipjaw pliers to back off the lockring, and with care you can get away using the large spanner from earlier on the flats. Risk here is that the metal flats are not large and can round off easily. Depending on how your bike was assembled, whether there is thread locker or some kind of never-sieze lubricant in the threads, and whether you ride it in the winter wet will depend how much force is required to undo this side. Sometimes they're barely finger tight.
The left side (non-drive side) is generally conventionally threadded too, so "right-tight/lefty-loose" Check here for better info https://bicycles.stackexchange.com/a/50365/19705
At this point the axle should slide out the NDS along with a cage of bearings or some loose bearings.
To get the drive side off is harder because it seems to get tighter. Also note the drive side is LEFT HAND THREAD so you have to turn it backward to get it off. There is no lockring on the drive side, just the cup.
Engage the end plate with two flats like this:
Once its all clear, use something to clean out the housing. Rags, degreaser, even an old toothbrush work well. Do watch out for slivers of metal which can hurt. Take the opportunity to clean and wash the whole area hidden by the cranks, and check the frame.
Moving on to reassembly, the only extra tool not already mentioned is a BB tool which looks like this, and engaged the splines on the cartridge you bought.
BB cartridge fitting tool
Then fitting this is a matter of greasing the threads, insert cartridge from the Drive side, tighten quite a lot, then put the little ring part in from the left side. Then refit your cranks with the new bolts that come with the BB
- Can I strip it or is better to just replace, if so, with what?
Just buy a new cartridge BB and fit it up. An old cup and cone bearing may be rejuvenated with new balls, but any damage to either bearing surface and you're replacing the whole thing anyway.
Cartridges are adjustment-free and a lot nicer to ride. You should get 50,000 km out of a cartridge.
You need to make sure the various specs are right. That's the overall length of the BB axle, the interface of the BB to the cranks, the diameter of the large threads, and the handedness of those threads too.
Notice the different fittings on the end. Your has to match your cranks.
- What should the torque be of the nut to hold pedal arms?
I'm sure there's a figure for torque, but in my experience its got to be "Quite tight" to stop fretting between the two metal surfaces. Try to gauge the pressure required to undo the fastener, and replicate the same level of tension when refitting.
To give words, I'd suggest a hand on each end of a 25cm spanner, but not using any kind of hammer or impact.
If you're unlikely to do this sort of work often, then there's little benefit in buying tools. Either pay your LBS to do the task, or search around in your location for a bike cooperative who will have all the tools.