Hello all, I've been looking all over the place (google and bing) and haven't found a thread or DIY guide on how to get this done; especially the rear struts; so I figure since I'm doing it let me go ahead and document for others.

I'm replacing both air struts on the RRS 2012 L320, the car was bought back in May last year and has been bouncy AF since the get go; kid you not; it's like steering a boat at times. Airbags are fine (no sagging in the AM) but the struts are gone. A couple of months back took it to LR here in Indianapolis and it is outrages what they want to charge for this bad boy to be back in a tip-top condition. $5500 for both; the free diagnosis from them (LR) was to indeed replace the air struts.
I’ve been documenting along the way; but here are the steps I followed:

1- Get a flat area to work on.
2- Disconnect battery. –I did just the negative.
3- Use either the 22mm or 23mm socket for your lugs nuts. Different theories as to why some are different sizes, not getting into that ATM.
4- Jack the car and user jack stands. I don't trust my 5 ton Jack, plus it's safe.
5- Remove the top 3 bolts.... yeah… it was not that simple....
Story telling time:
Car has original Struts (90k miles). 15 MM 12-pointbox, once you break the ol rusk; you’ll be smooth until you hit that Blue Loctite- or maybe it was the rusty tip of the bolt; wholly $h!T, good 20 min on each nut, no joke. I even paused to look up any good ideas to melt or soften this blue goo and some said heating it. This is where I got dumb … I somehow got my heat gun (in the tight space you have) to get the last inner nut; started heating the nut and created a hole on my air line ! .

Yes, loud exhaling from the airbag -Heating didn’t work BTW. So another 25 min getting that last one out.
Space was super tight.

Had to improvise and use a 2X4; about 2.5 feet long to push the wrench from the outside.

This took a while but worked. Careful with the force push here. You can end up slipping and going straight and breaking some stuff in there.
I end up buying Freeze-off, read the reviews on the product and seems like this might be something that will help. Fast FWRD and sure enough it did work. But what really end up fixing the whole bolt situation was to use a small torch can, from a soldering kit and also using a fine pick to remove rusk from the top threads, remember that’s been exposed for all these years.
I bought this air line hose repair from ebay
Fantastic repair for the small hole I created while using the heat gun.. LR has their own part but of course more money.
6- Remove long both from the bottom that hold the strut in place. Remove the Strut.
Note : on the Rear Driver side I had to remove the entire wheel well liner, careful as the TPM is attached to that liner, just remove all bolts in there.
7- Lower the strut down and carefully remove the air line hose, this uses a 12mm wrench.
8- Clean up anything you need to and get the new strut in place and do things in reverse order.
9- Prepare the new air line connector by removing the old one, careful here to not leave too much of the air hose as it might take you forever to get it to tread all because the hose tip was too long – yep I had that issue J
10- Get the new Strut in place. Make sure the bolts line up with the receiving end. Since the Strut is a bit heavy I used the jack to help raise it, just enough to get bolt’s treaded on. I suggest you get the strut in the bottom fitted first and get that long bolt in there. Once here, use the jack to raise the suspension so that the bolts are threaded all the way – use blue Loctite to keep things in place.
And that’s about it. Whole process did take me alone, in the cold and in my garage a good entire day. I triple check things all the time. But I’m happy with the results,
Note:
Once all it’s put back in place, reconnect battery; lower the car slowly and most likely the car will bottom out, start the car and it will ask you to confirm the desired high, I chose normal height, compressor goes off and the car leveled. I let it sit there for a while just in case something in the air line repair came loose and after a while took it out for a spin, nice little 10 min joy ride and all working beautiful. No more bouncing, car feels very sturdy and I’m a happy camper. This AM woke up, checked on the car and nothing sagging. So I’m glad to say things came out pretty good.
Parts I bought, that you can look up:
Ebay – Pair for 2006-2014 Land Rover Range Rover Sport Rear Air Suspension Struts. $381.92. make sure you get the ones with allow to return and seller pays for returns fees.
Land Rover Range Rover '03-12 Suspension Air Line Hose Repair STRAIGHT Connector $11.95 - sure a bit steep but it got the job done.
That’s it, thanks for reading, let me know if you have any questions.