Toyota Camry LE 2005 4 cycl 2.4ML, 17,000 miles.

Rear left plastic bumper side got pushed in by Pickup truck.
Was told that bumper needs to be replaced.
Bumper costs about $45.00.
To have it done estimate is $500.00.
Can I do this at home:
Unscrew the nuts holding the bumper to the car,
replace the bumper, tighten the screws?

Thanks very much.