Anytime you make a change to the rear end you need to run through the gear setup. Over the years I have seen running changes in bearing cone thickness, necessitating different pinion shims, and since you will not be able to reuse your factory side shims you will need to set the backlash again. I would never advise just throwing bearings in it and thinking all will be well.
A good master bearing kit is going to run you in the neighborhood of $200. I would only run Koyo, Timken, or SKF bearings. There are Chinese knock offs out there that are junk.
If you address it early on you can probably save your ring & pinion. Continuing to run with bad bearings will eventually cause a failure, lock up the rear and now we're into big money.
How hard is all this? Depends on your level of experience and ability to learn new things, plus what tools you have available. A press comes in very handy, but isn't 100% necessary. I rebuilt rears and transmissions for years without a press. You can cut the old bearings off with a whiz wheel and drive the new ones on with brass punches. A press saves you time. Making set up bearings is also a good idea. With a die grinder and a brake hone you can enlarge the ID enough to get a slip fit, allowing you to figure out shim thickness before pressing the final bearings on. To set the crush sleeve...no, don't use a crush sleeve, get a solid spacer kit for like $15. The crush sleeves cause a lot of rear failures. I've never been a fan. A solid spacer is a lot easier to get right because it isn't one time use. You will need a drag gauge or low reading in/lbs torque wrench (tricky, but works in a pinch). Old timers can do this by feel, but I need to check it somehow. If you feel like tackling it I can walk you through it. I've set up many rears, and have yet to have one fail or make noise.
'06 F250 4x4 - 5" Flo Pro exhaust, SB Filter intake, Accufab elbow, Edge Evolution (monitoring only), SCT w/ ID custom tune, FASS 195 pump, Gillette Diesel EGR cooler delete, Sinister Diesel coolant filter, ELC coolant, updated turbo drain tube/oil feed line/STC fitting/oil cooler, ARPs w/OEM HGs, Elite coolant lines, ITP RR fuel system, RCD 175/30 injectors, Powermax, BD CCV, FICM.com FICM w/ ID tune, Elite UP, BPD water pump - 13.069 @ 101.94
'02 WRX - Outback rear disc swap, EBC green pads, DBA pillar vane rotors, TXS UP/TBE/TMIC, Perrin LW crank pulley, PPG billet steel shift forks, ACT Streetlite flywheel & clutch, K&N filter, STi Group N motor/trans mounts, TiC/Kartboy rear diff mounts/subframe lock bolts/outrigger stiffeners, Kartboy SS & all shifter bushings, custom PDX tune for Cobb AP - went 14.1 on a terrible 60ft before most of these mods; shooting for 13.50s