Look at the 2 belts for the drive again. It sounds like one of your belts is rubbing a guide somwhere.
I am thinking the 1992 model would have bolts or pins around the engine pulley. and there is another pin by the variable speed pulley in the middle. Also, its easy to get the idler pulley on the wrong side of the rear belt. Rather than me try to tell you, best look at a parts diagram, it will be correct there.
MSRP List price for the genuine MTD spindle is probably over $100. It is for some of the later model mtds. The price you paid was probably for an 'aftermarket' copy of the oem part. It will probably work o.k. though.
For your front axle, I am guessing you mean the spindle on one side is wearing the bushings quickly where it rotates in the front axle. be sure it is not rusty. Rust will eat the plastic up pretty quick. Keep dirt off it when you assemble it. If the spindle is out of round or much undersize, you probably need to replace the spindle.