My 909 player has become noisy when a disc starts to play. If I eject the disc, and start to play again, it is quiet.
If it is the spindle motor, can I replace it myself?
When noisy, if I use finger pressure on the front left corner, that is, push up, it quiets down somewhat.
I've been told, that the chassis might be torqued. If it is, how can I un-torque it?

Your player just may not be sitting level. Make sure all the feet are making solid contact with the surface of whatever it's sitting on.

If you place it on a rug or carpet does it still make as much noise?

also you can get a square, the L shaped tool to see if your player is flat and not skewed

I always put a little sheet of that packing foam under the feet of my LD players. It damps down sympathetic vibrations.