Do I need any special tools or new bolts to install these?

You'll need basic hand tools and a socket set to unbolt the old hub. Mounting bolts are reusable if they're in good condition — inspect them before reinstalling. Torque specs are in your vehicle's service manual.

Can I install just one side, or do I have to replace both?

It's best practice to replace both sides at the same time for even braking and handling performance. That's why these come as a pair.

What's the return window if the bearing doesn't fit or feels wrong on install?

Test-fit the assembly on the spindle before fully torquing everything down. If it doesn't seat flush or the bearing spins rough, stop and contact support with photos of the mismatch.