Please keep us posted on this progress and list of items needed to change.
I'm looking at doing the same, but haven't had the time to tackle this with a young family. Good luck and hope it goes smooth for you.
So, I'm at a Toyota dealership with nothing but tine, chatting with the parts guys. We pulled up the sequoia on the computer, and compared the sr5 with the platinum.
Honestly, everything looks the same, even the lower control arm. They do have different part numbers, but look identical. Outside of that, isolator and spring were the only differences.
This may be an easy job to tackle afterall.