Replacing my locks/door handles
Yes, a novice handyman can easily replace door knobs and deadbolts.  All of these come with good instructions, so read and follow them and you will be fine.  In North America, residential door knobs and door locks have a back set of either 2 3/8" or 2 3/4" - the backset is the distance from the edge of the door to the center of the hole for the door knob or lock.  Measure the backset and buy replacements that will fit the same holes.  Note that many door knobs are adjustable so they will work with both backsets.

One thing to consider is the security.  Make sure the deadbolt strike plate in the door jamb has long screws that extends into the house framing that surrounds the door.  Also, don't consider door knob locks to be secure - they are not as they can easily be kicked in.  I always replace those type with a regular knob and a deadbolt.

BTW.... Good luck with the "unduplicatable" keys...  there will always be someone who is persuasive or will badger some poor person into duplicating a key stamped with "do not duplicate". Your best bet is to find a lock where the blanks are unique or not readily available.  I replaced the deadbolts on a house with Medeco a number of years ago.  (At that time, Consumer Reports rated them the most secure locks.)

Every manufacturer has different grades of quality, so it is impossible to say every product from manufacturer X is good quality, and sometimes the quality of the parts is reduced to save costs.  Read recent reviews for the particular model of lock you want to install.  If you are able to examine the components of the lock before you buy it, examine the pieces to see if they are just cheap stamped metal or if they are made of something stronger.