Hey Richard-D, funny I am on this too, found a good installer video (3 part) on youtube for a sequoia and speakers,
(part 1),
these guys are very good, I think he just won an award for installer of the year. Believe me I am handy and do most of my work on my 2002 1st gen but I am thinking about paying someone to do this for sure LOL. He uses an alpine unit but I purchased the Pioneer DMH-1500NEX from another video I found. I believe both are apple play compatible but realize that this is a plug in feature not wireless apple play, although everything else will stream. I did get the Kenwood speakers he mentions in the videos. I am still looking for a backup camera to integrate with the head unit, plus a USB charger/mount station for the center console before I seek out an installer. I would truly do this myself but I am sure it wont be at the level of a professional. Watch the videos and you will see that the wiring they create to adapt the new unit looks a little beyond my patients at my age LOL. Good luck. Let me know if I helped.
Ghost
2002 Sequoia Limited / 235,800 miles (1 owner baby !) Me