Even a set of big ****s cutters followed by dressing the end square and clean with a file works OK. If you do it by hand like this hold the end up against a bench or lightly pinch it in a vise so the end is just barely over the edge. Dress it with 8 or 10 strokes of the file to remove the crush distortion caused by the jaws.

Bikes shops typically carry decent basic lined housing and cables in bulk. So you don't need a kit but could just ask for x feet of housing and two each of shifter and brake cables. It shouldn't run you more than $12 to $15 to get them this way. Compare that to whatever kits they have.

If you measure all your bits and buy the housing in bulk be sure to get at least a few inches extra to allow for dressing off the ends.

Also since this is very likely a friction shifting 10 or 12 speed you can use the slightly cheaper brake housing. If it's been upgraded to indexed shifting you'll need to stick with the "compresionless" shifter housing. Be sure not to get the two mixed up when installing them.

Kits at bike shops tend to be the more deluxe stuff. And kits at the local Wally World or similar tend to be the bottom of the barrel stuff. It's worth it to pay in the middle and get a basic kit or buy the bike shops bulk items.

And don't forget the end ferrules and cable caps while you're at it.