BTW they are small, plastic, yellow, and rectangularThose sound more like capacitors, either electrolytic or tantalum. If they look like
these then they are caps.
The board may work without them, but will not be very reliable. They are mainly used to filter the power.
If you try and repair it then make sure you get them the right way around. Electrolytic and tanalum caps will explode violently if powered up backwards (or if the rated voltage is exceeded).
To fix it you will need a good soldering iron (a cheap 25w one will not work very well and will likely damage the board) and a steady hand. A magnifier, tweezers, etc. also help.
If the pads pads are missing try to follow the trace to the nearest point you can solder to or scrape off the soldermask (as mentioned above) and attach the cap with some wire. Look for nearby caps that connect to the same power source. Keep your wires as short as possible to minimize the effects on the circuit.
When you are done use some glue to hold everything down.
