Boardman mtb txc 650b team hardtail 2014.

Hi
My myb is getting on a bit now and has started to make squeaking noises now from both from and back wheels. It's not the pads touchthe rotor blades, I've oiled the spindals. I come to the conclusion now it must be the wheel bearings. I want to change them ideally to sealed bearing if it is a straightforward swap out. Can someone help and advise what tools and bearings to purchase? I know I'll need a speacial nut to remove the rear cassette.

Thanks