As chelboed said above, some pivot bearings need specialized tools to remove, depnding on the bike. BUT, there are many "special tools" that you can replicate with odds and ends in your home shop to make quickie bearing presses and do the work yourself. About the only problematic bearings are those pressed into bores that have shoulders or are blind that make it difficult to drive back out, especially if the old bearing is shot or disintegrated.

Most suspension bearings are standard metric cartridge bearings available readily at industrial bearing supplies. Oftentimes too, you will find you can get a better-quality replacement at the bearing house than the stocker the bike came with (higher quality seals, etc.) - - since many companies use the cheaperst off-the-shelf bearings they can find.

Keep in mind too that most ball bearings used in suspension pivots were originally designed for relatively low-load/high-RPM rotational loads and, so, will not always lasst more than a few seasons in a mountain bike frame by the nature of the loads they are subjected to outside their intended design. But, at a typical $5-15 a pop to replace, depending, that's not a bad lifespan.