The door leading outside from my garage has two holes for locks -- the
top one is the kind with a lever, up is unlocked and down is locked.
The lever is on the inside.
The second hole just has a door knob - no lock - and it has broken
off on the outside. The knob came off and is just sitting there on
the stem. The door still locks fine ... but it looks bad and I want
to change it myself.

If I buy just the bottom part - it looks like the kind that is used
on interior doors - no keys. How hard are those to install? The one
that is on there has two screws.

I can call a handy man service to come out and do it but would like to
save the money if I can. Thanks.