Jim,
You really can get great images out of that lens you already have! Don't give it up so quickly. The first zeiss lens I ever had was that very model, an AE 50 1.7....matter of fact I still have it. Got it in '86 when I first took up shooting and was away at school. If you have an RX, great .... just try again, really, you'll be surprised. Shooting on P mode should be forgotten anyway, no great images are ever made in P full auto mode except by rare accident.
To aquaint yourself with the camera and lens combo, start shooting in Aperature Priority (AV). Now, do not depend upon simply turning the dial to AV and setting your aperature and just shooting anything that crosses your path, you still have a little thinking and work to do to produce the stellar images that the glass in that lens can regularly produce.
Take a small notebook, pen, roll of slide film and your camera and lens out for a couple hours. For every scene you want to shoot with this roll of film, you will make several exposures and adjust each shot moderately according to what the meter tells you. For ex&le, if you are shooting a blackish animal against a well lit background, spot meter the blackish animal, and take your first shot. Now, based on that first reading, using your exposure compensation dial, take a series of other shots at -1/3 stop, -2/3 stop and -1 stop, then go the other direction and add 1/3 stop. Record in your notebook which image corresponds to which bracketed shot, and later when you get the slide film back, you will understand how to compensate for what your meter is telling you. (I suspect either the -1/3 or -2/3 will be appropriate for a black animal).
Note that if your subject is white, or lighter than a grey card when you are spot metering the white segment, you'll want to add 1/3, 2/3 and a full stop (or more!), but rarely will you need to subtract anything with the compensation dial.
Make sure you use slide film, because you can see your exposures perfectly, whereas with negative film you won't know what the processing person has compromised for you.
If you want to know more about this, there was a great newsletter a friend gave me years ago that a friend gave me on this subject, I can't remember the name of it, or the photographer who wrote it just now, but it was gold for me in understanding how a metering system interprets the world.
So, please don't throw out your existing lens, it is just a matter of using it to your best advantage
Good luck!
-Lynn