A lever handle is easier to operate for a parent whose grip is weaker, and it is a small job that goes wrong at the measuring step. Most of the work happens before the screwdriver comes out. Measure the door, check the existing hardware, and confirm the handing before you open the box.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Measure before you buy
Measure the backset, which is the distance from the edge of the door to the center of the existing knob hole. Measure the door thickness and the hole size if the door is already drilled. Note which way the door swings and which side the handle sits on. Write these numbers on the box so you buy the right set the first time. Ask the store whether the set can be returned if the measurement turns out wrong.
Check the existing hardware
Remove the old knob set and look at the latch and the strike plate on the frame. Note whether the latch is spring or a deadbolt, whether the strike is aligned, and whether the wood around the strike is solid. If the frame is split or the strike has already moved, fix that before you install a new handle, or the new one will sit crooked.
Gather the parts and tools
Gather the kit parts, the template that comes with the set, a screwdriver that fits the screws, a tape measure, a pencil, and masking tape. If the set needs a new bore hole, you will also need the right drill bit and a clamp. Lay everything out before you start so you are not hunting for a part with the door half off.
Install step by step
Hold the template against the door face and mark the holes. Drill the cross bore to the size in the instructions, then drill the latch bore through the door edge at the marked depth. Sand the edges so the latch slides cleanly. Insert the latch so it sits flush with the door edge, then fit the outside lever and the inside lever over the spindle. Tighten the screws evenly, a little at a time, so the lever sits level without squeezing the latch. Set the strike plate so the latch clicks in with the door closed.
Test the handle
Press each lever all the way down. The latch should retract fully and the lever should return to level. Test from both sides of the door, open and close it several times, and check that it closes without rubbing. If the set has a lock, test that from both sides. The door should latch on its own without a push.
Know when to stop
If the frame is split, the strike will not line up, or the bore has drifted enough to weaken the door edge, stop and call a handyman. Do not force it. If the door sags after the install, that is a different problem, and tightening the handle will not fix it. Note the details in the same folder as the other household papers so the next person who touches the door knows what was done.
The job often takes longer than the box suggests, so schedule an afternoon for it. You are allowed to leave the second door for another day. One door done well is a better result than two done in a rush.