So I just did this repair. After following the instructions to get the display assembly off of the body of the laptop the next thing to do was figuring out the how the cover would come off.
Like the first poster stated the end caps are adhered with glue and also have a small ball on them that fits into a socket on the clutch cover. The best way to get this off is to place the tip of a spudger in the gap between this small end cap and the clutch cover on the bottom edge of the display. After prying out the bottom part of the end cap the top part with the adhesive is easier to get off. I used a little heat just to make it all go a little smoother.
After taking off both end caps the entire clutch cover needs to be slid towards the side of the display with the air-port and camera cables. It takes a little bit of work but it is manageable. After the old one is off I had to reseat the air port antenna because one of the brackets had come loose and caused it to protrude down, breaking my clutch cover to begin with.
Assembly was the reverse of all the steps. Use the cut outs in the display to line up the clips with where they need to go. I bent a couple of mine out of shape on the first try but using a case opener tool I was able to get them lined up and slid the clutch cover back on. The end caps are a little tricky to get back on. For me they clipped back together the best when seated the end opposite the ball and adhesive before pushing the ball back into place. Make sure that everything sits flush and perpendicular to the edge of the computer before putting the display back onto the case since if its a little off it will rub or get jammed. It is worth taking the extra time to get everything back the way it should be.
Below is the cover I ordered off amazon. Make sure the one you order is for your model number and I like to find items fulfilled by amazon because I've found the sellers that take the time to stock things at Amazon's warehouse are more reputable than ones who ship from china. Also FBA gets prime shipping which is really nice.
[https://www.amazon.com/gp/product/B017E1N6SA/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1|MacBook Pro Retina 15" A1398 Clutch Cover]
Make sure you have a good set of tools, like the Pro Tech Toolkit, and the skill to use them. All the work you will be doing is very delicate and in a sensitive area. If you damage the things under the clutch cover you can loose wifi, bluetooth, ect. Mainly just go slow and make sure your doing everything as carefully as possible. You don't want to destroy a $400 display assembly trying to replace a $15 cover.
Overall I think it was worthwhile doing the repair. The new cover is doing a better job of keeping dust and dirt out of the antenna area and it just looks way better.