Cable cutters, not dykes. You need round things to stay round. Bike are a good excuse to buy tools, most things aren't too expensive.
I prefer Jagwire, plenty of kits on Amazon or at your local shop. They can also cut housing to length (it will most likely be Jagwire they stock by the spool) and sell you the cables, but you won't get all the ends and spacers in a neat little kit.
Derailer B tension should stay the same, adjust upper and lower limits and set the barrel adjusters. Brakes are easy too.