Disc brakes..That's a job, and pricey.
Unless your frame has mounts, they'd need to be added, which is expensive.
You'll need a front fork with the mounts, you'll also need front and rear hubs.
If your bike has all that, great, if not...
It adds a lot of stress to your wheel, I think mainly just the hub, don't quote me on that.
Get some Kool Stop pads, the salmon color if you're planning on riding in the wet, or are worried about puddles causing your brakes not to work for the first few seconds. Dry stopping power is comparable to regular brakes, maybe slightly less grippy.
I've noticed hardly any wear on mine in 200 miles, I'm a big guy (250lbs, 6'9") and normally tow ~80lbs in kids and gear, so they should last an average person a good long time.
LBS's get them for about the same price as online, and they'd be sure to get ones that work for the style of brakes you have, so it's worth the $1-2 extra.