Behr is what was fitted to the series 3 Spiders, and the set-up where the top screw is covered is how they came. If anything, it's evidence that the speaker and A/C are unmolested... That also means that you are in for a frustrating time, but believe me, you can get the screw out... It's a royal PITA, and it's been a long time since I've done it, but it does come out. I don't recall using anything too special, beyond a mini tool with an offset to access the screw. Then I know I pried the A/C unit just a tiny bit with something like a very long heavy screwdriver, and pulled the screw out. Of course you could dismount the A/C, but I didn't have to... When you go to fit new speakers, you will need to make sure that the speaker grilles are very thin, or the one on the passenger side won't fit...
Best regards,
Best regards,