How do I replace the bobbin case on my singer 5050?

It's on page 56 and 57 of your user's manual, with drawings. You can download it free at the Singer Sewing machine website.

is this a top or front or side loading bobbin case?

I think this is your bobbin case
http://www.sewingpartsonline.com/bobbin-case-apollo-singer-421326.aspx
being plastic they are damagable if the case moves and the needle strikes it. Sometimes you can file out the damage with a nail file. But replacements are available too.

Hope this helps.

Go to www.sewingpartsonline.com and order one from there.

Top tension about 4 or 5, use a good mercerised thread only, make sure you do not have the bobbin tesnion too tight, slacken the screw anti clockwise on the bobbin case if it is

Unless you are going to hand wind a heavier thread on the bobbin, you do not need to make any adjustment to the bobbin tension.

There is a screw on the side of the bobbin case and this is where you adjust the tension.

You can download a free manual here - http://www.singerco.com/accessories/manuals.html

If your stitching is loopy, it is not the bobbin.

Re-thread the machine with the presser foot up. This will insure proper tension when the top thread and bobbin thread combine to make a stitch.

The silver plate should be on top.

Take out your bobbin case... there should be a small screw fixture on the side of the case...turn screw anti clockwise until you get the correct tension ... To test the bobbin thread tension...Remove the bobbin case keeping bobbin attached and hold it by suspending it by the thread...**** it once or twice, if the tension is correct the thread will unwind by about an inch or two. If it does not unwind at all...tension is too tight. If the tension is too loose it will drop too much. Goog Luck

your machine sound like it is out of time you need to take it to a service center

If you put the bobbin in the case with the thread coming off in a clockwise direction, the thread should just fall into a slot and gently tug on the thread and it will slide through the tensions. Lay it across the bobbin case and then pick up the thread with the needle.