Getting a programmable remote is one way to solve the problem but the functionality and locations of the keys may not be satisfactory.
Repairing your remote should give you more satisfaction as you get to keep the remote you are used to.
Common faults are: some buttons not working, not working at all, corroded battery terminals. Often buttons are sticky because of some dirt accumulated over the years from the sticky little hands of your kids?
The hardest part of repair is often to open the covers. You do not need much experience in electronics repair to repair a remote. Also it is perfectly safe as there is no way to get an electric shock as they work with batteries.
Step 1: Test your remote with Digital Camera
Step 2: Open the remote control but there is a catch or a few catches.
Step 3: Take a picture of every phase so you remember how to re-assemble
Step 4: Pull everything apart
Use a small plastic takeaway box or similar to store the bits so you don't lose parts.