The parts that you mention are on the 'DM' circuit board, and the Yamaha part numbers as shown in the Service Manual are ...
C0000 Electrolytic Cap. 100.00 (uF?) 25.0V Yamaha part: UR848100
IC114 IC SI-8050S(LF1111) DC-DC CONVERTER Yamaha part: X0548A00
The part no. for the complete PSR-2000 DM circuit board is V7637800
The obvious way to try to source the parts is by contacting your country's Yamaha Support operation.
This is an old keyboard so I don't know if Yamaha can still supply the parts! The capacitor would be easy to source elsewhere, but I don't know about the DC-DC (Buck converter) IC114. However you will find data about it if you 'google' 'si 8050s regulator' or similar, so you may be able to source it.
If you can get new parts, assuming that you have some experience at soldering electronic components, they don't look to be too difficult to replace once you have removed the board. Neither component is a 'surface mount' type and the IC is just five pins in a TO-22 case. The Service Manual will be helpful in dismantling the unit.
Regarding whether this is a logical repair, that's anybodies guess, but the two components are next to each other on the circuit board, and if the IC is not outputting +5V DC from pin 2 for some reason, the keyboard is unlikely to work!
I don't know if this helps you at all!