Replacing bifold door hardware is not difficult. You can purchase both individual parts and complete kits for bifold hardware. Try to isolate which part is bad and find a matching component.
Before you assume that you need to install new hardware, you should see if the door can be repaired. See the articles 'Repairing Bifold Doors' and 'Adjusting Bifold Doors' for information on getting an existing door working properly.
How the Hardware is Installed
The pins and rollers are press fit into the holes in the door panels. The tracks and base clips are screw attached to the door frame and floor. There are also hinges and alignment clips, these are screw attached.
New Bifold Hardware Cost
Replacing bifold door hardware begins with a new kit. You can get a complete hardware replacement kit for between $15 and $30, depends on the size of the door. Individual parts can be as little as a couple of dollars. Before you buy anything, try lubricating the parts. Step Five talks about this. Although it's a simple concept, if it moves, oil it.
Installing the New Hardware
When you purchase parts, you will probably get some instructions. I hate to say this, but take a look at them and follow the steps. I consider myself fairly handy. I wish I could get an accurate count on how many times I have tried to install something, messed it up and humbly had to go back and check the instructions. Save time, take a look at them. The parts for a bifold are pretty straightforward, so I am not spending a lot of time on them. After you have installed the hardware, you can pat yourself on the back. You have completed an interior bifold door repair. Well Done!