if its really bad

remove 2 screws holding door handle
unscrew and remove plastic lock unlock tab at the top of the door

CAREFULLY *************** remove plastic door handle surround...very brittle crap
use NO screw drivers for this.....something thin and wide to slide underneath

use same tool as door surround to slide between door panel and door frame to unsnap the holding clips....expect to break a few unless you are very careful

carefully lift door panel upwards to break it free of the two metal tabs which hold it to the door frame just just under the window opening.

once loose carefully remove 2 door speaker wires from speaker

the motor is now visible at the bottom the door frame.

i think it has 3 bolts holding it in place. remove these and then cut the motor wire leaving enough wire to splice ion the new motor wire. you will have to jiggle/wiggle whatever the motor out of the regulator gearing but its pretty self evident once you see what is there.

I haven't replaced a motor, but before you do make sure it is actually defective by putting voltage directly to it. (It may be a switch instead.)
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1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.