1999 Cavalier Wheel Bearings

I have a 1999 Cavalier & up until a week ago was quiet! Now anytime I am braking or making a right hand turn (with my foot off the brake) there is a horrible screeching noise. I have had a friend look at it & he says he thinks it's my left rear wheel bearing. Is this something that can be done by yourself or would you recommend taking into the shop? If it is something that can be done outside the shop how labor intensive is it? How expensive (ball park figure) on if I took it to a shop? We are hoping to repair this sometime this week please let me know at your earliest convenience. Thank you.