Replace Bumper Cover help

[bepop&rocksteady]

Hey everyone,

So I am looking to replace the bumper cover on my '09 Matrix AWD because I pulled off the drivers side corner with another car while backing up (probably my most embarrassing moment ever). Anyways, a friend was able to do a quick fix of it and it looked just fine other then some ugly deep scratches on the bumper cover. Just a few months ago as I was driving down a highway, the plastic over that starts inside the wheel well and goes under the vehicle gave out (because the clips I had damaged the clips) and became shredded against the tire as I was driving.
So now I have some extra money and I would like to buy the right parts and get fix it myself to save my self money other then going to an auto body shop.
So my questions are:
1. Should I do this myself or just pay extra money for a shop to do it?
2. What parts do I need other then the bumper cover and the other piece (Anyone know what this is called?)
3. And, is okay to buy parts online? Any recommendations for online places?

Thank you for your help!

P.s If needed, I can post photos for further clarification

[milkyway]

please post photos to make sure which bumper parts you are talking about......

[bepop&rocksteady]

Thanks, I think that is the best way.