If you have standard ‘cheap’ locksets, it is very nearly cheaper to replace them outright than to try and re-key them. If you have good-quality locksets with threaded cylinder keyways, it is an easy task. You would go to your local lock-shop and purchase sufficient cylinders keyed in the way you wish and then simply swap them out – installation and adjustments take about 15 – 20 minutes per lock (just be sure that you get the correct-style cylinder as they vary). Similarly if you have a restricted-keyway system such as Best or Medeco – only in these cases you would replace the insert only which takes no time at all if you have the release-key. Some very few lockshops will give you credit for your old threaded cylinders if they can be re-used – ours does, for instance.
Bluntly, attempting to re-key a standard residential-grade lock is just silly based on the actual replacement cost.

Yes, if you’re a locksmith. Re-keying a lock cylinder is not something you can learn how to do properly just by watching a couple videos. It takes a lot of practice and I guarantee you’ll lose a few pieces on your first couple tries. Those springs maintain enough pressure to shoot a pin across the house and have you searching for hours. Save yourself the hassle and just buy some keyed-alike cylinders (check your locks to see if they are Schlage-type or Kwikset-type cylinders first, then go buy). Some hardware stores and all locksmiths will sell you those. It’s much cheaper to install them yourself, so try that first. If you want to just go the route of buying new hardware (bolts, knobs), I would suggest the new Kwikset SmartKey deadbolts. They have an ANSI Grade 1 rating (if you install the extra back plate with the 4″ screws), and can be re-keyed at home in seconds. These bolts can be purchased at HD or Lowe’s for about $30-$35 each. I use these bolts on my own home and they are excellent. The last time I needed to change the key I bought the $10 re-key kit and changed them all in less than 5 minutes (3 bolts). Please see the link for more product information. Hope that helps..

If you want to change all of your hardware, you can go to a home center and have them all keyed alike, then come home and change them. If you want to change the cylinders in your existing locks, call a locksmith. It’s not something you can learn in a day, and the investment in tools would exceed the cost of a service call several times over. Hope this helps.

Yes it is easy, for dead bolts, door knobs are a bit more difficult. I don’t know were you live, but if there is a Lowe’s or Home Depot near by they have kits to do just what you are asking. The Kits will include new Keys and little Pins that you will change out in the locks.
Tell them what brand of lock you have and how many you would like keyed the same.
I have done this for myself.
If you don’t have a Lowe’s or Home Depot a local Hardware Store or Locksmith should be able to order them for you.
Youtube has videos to show you how. Type in Rekeying a lock

No! Not only do you need the right equipment, but you need to be trained to do it. That’s why locksmiths go to school for their profession.

It would be a lot cheaper to buy new locks and install them yourself. The ‘book of words’ that come with the lock set are quite good.

Re-keying is a trade. I see new locks on the market that offer a simple process but they are cheap locks to begin with.

Generally yes, I put new locks in my house when I bought it. You can get a good set at home depot.