Damaged rear bumper spoilers and lower engine cover

A few weeks back, my Prius got stuck in some gravel and dirt off the side of the road. The wheels just spun and created ruts as I tried to drive away, so I had to get a tow truck to pull the car out. In the process of getting pulled out, the car sustained some damage to the underside coverings. I took some pictures of the damage (see attachments) and showed them to the dealer parts department. They gave me a list of replacement parts, and I took some time to get some competitive prices:


All prices are for new genuine Toyota parts

I think rear right-hand bumper spoiler has been vibrating at low ICE RMPs, and is rather annoying (it definitely seem to be coming from the right-rear section of the car), so I am inclined to replace it. Beyond the vibration, I’m not sure if there are any mechanical or safety considerations that would warrant a replacement.

The rear bumper spoiler seems completely cosmetic. I can’t think of anything that would get damaged as a result of not replacing it. It is a bit of an eyesore, however, and at under $57 on ebay, it just might be worth it.

Cosmetically, the lower engine cover is “out of sight, out of mind.” However, should I be concerned about foreign objects being thrown into the rather large voids and causing possible damage? This seems to be the cheapest of the parts, so I will consider replacing it even if leaving it as-is is no cause for concern.

Finally, there is a small flap in front of the right-rear tire that seems damaged (see “unknown part” picture). The parts guy could not identify this part (which may be my fault, as I might have erroneously told him that it was behind the right rear tire).

At this point, my inclination is to get the parts as cheaply as possible and install them myself. I am relatively mechanically inclined, and the job does not look particularly intimidating.

Questions

1. Should any of these parts be replaced immediately per some safety or mechanical concern?
2. Is $152 for all 3 parts (via ebay) a good deal? Should I look for better prices at a junkyard?
3. It looks like I may need to remove some additional parts when replacing the lower engine cover. Do I need to remove the bumper cover or other surrounding parts? I did manage to find an old post which says:
   
   
   This seems to indicate that the bumper cover needs to be moved out of the way temporarily, but not completely removed. Is this correct?

If it helps at all in assessing the situation, I don’t mind getting back under the car to take more pictures and/or take a closer look at something. Any feedback or suggestions would be most appreciated.