Stop worrying and do the update.
Copy down your settings first -- all of them as some defaults have changed since your firmware. AFTER the install, do a Reset Defaults -- the player should offer to do a Recommended Reset on the first power up after the install. Then re-enter your settings.
Since your firmware is so old, check that all the pieces of firmware are up to date after the install: Main, Loader, Sub/MCU. If any were not updated, repeat the install until you've got all of them. Check the version numbers in Setup > Device Setup > Firmware Information against the ones on OPPO's support page for the 103:
By the way, you only have to do that 0515 install -- not each of the one's you skipped. It incorporates all those as well.
Bugs will always be with us, but there are NUMEROUS important fixes in the firmware releases since the one you are running, as well as new features -- one of which is the added ability to save and restore settings via a USB stick, which makes doing future Reset's a snap.
The only significant feature that has been dropped is the ability to play SACD-R discs that you burn yourself.