Working on this car isn't any different than any other rear drive car except is has an independent rear axle. ( same axle shaft setup as a front drive car for the most part )

If the axle to differential bolts have a hole in them, they are XZN / Triple square .

If the bolts have a hear like a regular bolt but look splined, that is an inverse Torx. For the most part a regular socket / box wrench can be used, try a few sizes.

Does the noise sound like a screw driver being dragged across a fine tooth gear as it is spinning? Sort of an even fast tempo ZZZZZ sound.

These transmissions have a bushing between the input and output shafts, this wears and allows a needle bearing thrust washer to come apart and the metal parts get jammed in the planetary gears. These needles are about 1/8" dia x 1/4 " long.

When you say the shifter is loose feeling, is it looser that before the problem? There is a pinch bolt inside the trans that holds the lever to the internal linkage that might have come loose. This might cause the parking mechanism to jam.

With both rear wheels elevated and parking brake off, can you turn a wheel? Can you turn the driveshaft?

Don't randomly buy parts, diagnose first.