These brake pads are use on the parking brake (rear wheel) of my recumbent trike. Therefore, they will not get as much wear as normal brake pads. I expect them to last a very long time-barring any chipping or damage. They are very easy to install.
You can do it. There are tons of videos on YouTube to walk you through it. I have used both the organic and metal pads and really prefer the organic-much smoother and quieter.
With the bike shop all backed up with bikes to repair I decided to try to replace my own brake pads. I watched a couple youtube videos to figure out how to do it and all went fine. I now have new brake pads and feel empowered to do more of my own repairs and maintenance.
I use Avid JuicyBB7 Disk Brake Pads on my Volagi Liscio & Trek Portland. I can break with much more finesse i.e. don't over or under brake. Perfect on wet Portland streets. Also a big plus on a huge downhill run where caliper brakes are smoking and overheating the rims, the disk brakes have no probs.