Drivers rear wheel hitting side of wheel arche

worn trailing arm bearing better to fit second hand rear axle beam

Would it be a big job??

to replace rear axle beam in a garage i would say you are looking at about 3 hours labour providing mountings and brake pipes are ok and your original brake shoes wheel cylinders and drums are re usable .i am not sure how much a second hand axle will cost but make sure you get a good one to have the original bearings replaced is a big job requiring special tools and usually the bearing surface on the trailing arm is worn and pitted .