Hi,
if you go in there, renew also the flex tubes to calibers as they are 15y old and may not be equally open for fluid flow on both sides. If this is the case slowly baraking is more equal than fast emergency braking as no fast fluid movement is possible inside old tubes,
br tapsa

You might want to check the right caliper, it might be frozen. You will notice this when you replace the pads.

Brake squeealing is caused by loose pads vibrating and is usually the rear brakes.

When you remove the front brakes, make sure you clean and grease the slide pins.

For the rears, get new pins and spring clips.

Klaus
--
Proud owner of a 1967 220S

I would go ahead and just bleed the entire system if you can. This will help you avoid future problems.
PBR/axis makes a good pad. You can pick them up from import parts stores or fcpgroton.com Make sure you have shims. I like to stay away from putting grease near my brakes, call me crazy, just don't think grease should go near something that utilizes friction to do its job!

Before you start replacing things, note any abnormal pad/rotor wear. If the parts on the left side don't match the right side, you might have bigger issues.
Best of luck