new laser/assembly for Cary 303/300 cdp

The SL-710A drive can be found in some very inexpensive dvd players. My Resolution Audio Opus 21 also uses that drive. When mine was having trouble I did a lot of research trying to find the drive at a reasonable price. My research also showed that drive to be a fairly problematic drive.
Ended up buying what was claimed to be an almost new dvd player on ebay that had that drive in it. Sure enough for about $30 I had a like new transport ready for install from ebay.
Unfortunately, I threw the case away or I'd take a look and get you the model number. Google is your friend if you decide on that route.
As for cleaning the lens, I'd take a qtip with a light alcohol dip and swipe it. Be CAREFUL though as it is delicate. You can also get a can of compressed air and blow GENTLY at the lens. Good luck.

I haven't removed the end piece from my Opus 21 but did take off the piece from the drive that came out of the dvd player. I don't really remember how difficult it was but the drive is intact so it must've been fairly smooth.
The Apex AD-3201 is the model that uses the DSL-710A drive.

Go for it.

Here's an ebay auction for anAD-3201.
Might be worth a try.

You might try swapping the laser assy into the original drive mechanism that came with the Cary. I have replaced laser these lasers (not SL-710) and they are not difficult. If the original drawer works smoothly, this may be an option.

If this is the CD50 you're referring to, it was mine. I sold it for $350 about six months ago.