How can I stop a leaky Delta sink faucet? We have a more or less new Delta faucet, and it have...

We have a more or less new Delta faucet, and it have a slow drip that can't be stopped. Sometimes it is even a small steady stream. It has the one lever that go to the right or left, depending on whether you want hot or cold sea. I assume these are all washerless, so I don't know where on earth to start. I haven't taken it apart yet. Would approaching some answers before I attempt that. A professional licensed plumber installed it. It also have the hand-held faucet part that comes out of the mount and switches to a sprayer. I'd approaching to fix it myself if possible.
Answers:    Delta faucets own replaceable parts under the button

you need to remove the pedal, you will need an allen wrench of correct size
verbs the handle bad
next you call for to unscrew the cap surrounding the stem that the knob attaches to
use a wrench(I'd wrap a towel around the cap so you don't scrape the chrome)
under this is a plastic and rubber gasket over a stainless stem
remove these and near will be two black rubber gaskets on springs where the hot & cold dampen enter
I'd use the allen wrench to pop these out---these are what are causing the bleed

you should be able to buy these replacement parts at you local home expansion store or local Delta wholesaler

when installing these new pieces, align them on the allen wrench so you can guide them into in that respective holes
they then entail to be pressed down so the the rubber caps are tight on the springs and not sticking up to far (check the matured ones for reference past removing them)
then install the stainless stem, it will enjoy a slot in the side that must be aligned on a small tit inside the cavity
the plastic and rubber gasket go on top, this has a plastic tit that must be aligned within a slot where the threads for the bonnet are
then slowly screw the panama on so as not to turn the stem or plastic piece
tighten with a wrench, reinstall the touch and you should be back contained by business
it is time to retire and get a kohler.