I don't think there is much hope for the selenium meters. The newer MR and MR-4 are usually pretty easy to repair. I've done a bunch of them and usually it's something simple (though it's been a long time since I've had one apart).
I think the MR-4 meter is vastly underrated. The meter has a balanced bridge so a silver oxide battery works fine, sometimes requiring zero adjustment with the screw by the hotshoe. Since it coupes with the speed dial and covers the area identical to the 90mm frame lines it can be very accurate. For street shooting you can point it the subject (while the camera is at waist level), set the aperture, pre-focus by DOF, then quickly bring it up to your eye and shoot.