I'm assuming that you are already using an Oppo player (either the BDP-93 or the 203) with your older receiver and that you are using the RCA analog outputs on the Oppo to the RCA analog inputs on your receiver. And that question three is in regard how to deal with the audio output on your proposed region A player. And if it's a generic Panasonic player, it most likely does not feature RCA analog outputs.
Perhaps I can offer another option on how to stream your audio to your receiver from your region A player (either your repaired BDP-93 or a new Panasonic).
My current set-up uses an older pre-HDMI receiver and an Oppo 103 as my main bluray player. I use the Oppo 103 to decode the various digital audio formats, convert the audio from digital to analog, and output the multi-channel analog audio using RCA audio cables from the Oppo RCA outputs to my receiver.
I connect additional disc players in my set-up using the HDMI Input on the back of the Oppo 103. For example: I connect my Samsung HD-DVD player using an HDMI cable from the output on the Samsung to the input on the Oppo. This streams both the video and audio from the Samsung through the Oppo to my TV and my receiver. This also allows me to use the video processor in the Oppo to improve the video from the Samsung and it also decodes the digital audio format from the Samsung and converts it from digital to analog and outputs it to my receiver via the RCA cables. The Oppo does not passively pass the video/audio directly through. The video/audio is effected by how I've set-up my Oppo. In order to watch the Samsung I need to power up the Oppo and use the Input select button on the remote to select HDMI IN. Since I have a satellite DVR and two additional disc players I use an HDMI switcher between these devices and the Oppo (my switcher is 4 inputs going to 1 output)
In your situation the Oppo 203 has an HDMI Input on the back. So hook-up an HDMI cable from the HDMI Output on your region A player to the HDMI Input on the 203. You can then play around with the set-up features of both the 203 and the region A player to see what works best. The only inconvenience is that you need to power up both players and use the Oppo remote to select HDMI IN.