Replacing the kitchen sink is one of those jobs that you should not start until you have plenty of time and you should plan on a number of trips to the hardware store. The odds are the new sink will not be quite as deep as the old one, the drains may not be in exactly the same position, the faucet will be mounted higher, and something will break when you are taking it apart. This is also a good time to replace the faucet if it is showing its age.
Mark the water lines for hot and cold, shut off the water, at the stops (if you have them, otherwise turn off the water supply to the house – a good opportunity to install stops), and take all the lines loose.
Remove the disposal if you have one. Loosen the clips around the lip of the sink.
Carefully use a chisel or scraper to break the old sink loose from the dried caulk that is probably holding it in place.
Check for the fit of the new sink and enlarge the opening as needed. Caulk the underside of the lip of the new sink with a good silicone caulk designed for kitchen use and set the new sink into place.
Get under it and fasten the new clips in place.
Re-attach all the lines etc. and you are done.
I may be slow, but would expect to spend all day on this, assuming not too many things go wrong.