the KYB complete front coil over shocks are direct bolt in, there is no need to modify anything, they bolt right in in place of the originals & include new springs pre installed. if you have xreas the shop just wont be connecting the fluid lines. if they wont remove the lines you can do that very easy after install.
as for springs, if yours arent sagging or were abused with off roading or heavy towing you dont need new rear springs, the factory ones are perfectly fine for the street driving you said this will be for. some guys buy FJ springs for added lift but it doesnt sound like you want or need that, stick with the factory rear springs or buy OEM new ones for a 4runner, moog are the best OEM replacement.
your parts list has KYB mount kit... thats not needed when you buy the complete shock/spring, they come with the mount kit pre installed. look at rock auto or even amazon, they will show you the part# for the front L&R complete shocks/springs & the rear shocks. thats all you need unless you want/need to replace the rear springs & chances are you dont. i replaced fronts & rears & kept the stock rear springs with 140k miles on them, the rear sits nice & tall just like when new, rear springs dont go bad at ~150k miles & unless you want more lift or off roading you dont need FJ or any other aftermarket spring.
try searching for the complete front shock/spring assembly for a 2008 4runner, if you cant find teh part# i can post them or another member can.... keep it simple for simple on road use, no need to pay more for things that arent needed.
EDIT: looks like rock auto is out of the 4WD kyb front shocks/springs & other places are back ordered as is the case with many auto parts right now due to the virus crap. but i did find a couple places that have them on a google search, shock surplus looks to have all 4 as a set & summit has individuals with a couple weeks out for ship date. call around to the places on this search & see what you can find. also the shock surplus link shows the complete front set up i mentioned, no mount kit is needed for these.
https://www.google.com/search?q=2008+toyota+4runner+kyb+shocks&source=hp&ei=C0zDYeSjEo3atQbez5UQ&iflsig=ALs-wAMAAAAAYcNaG5RONDhDxCtjE-kHhR6z37r6ldXZ&oq=2008+toyota+4runner+kyb+&gs_lcp=Cgdnd3Mtd2l6EAEYADIICCEQFhAdEB4yCAghEBYQHRAeOggILhCABBCxAzoLCAAQgAQQsQMQgwE6CAgAEIAEELEDOg4ILhCABBCxAxDHARDRAzoFCAAQgAQ6CwguELEDEMcBEKMCOgUILhCABDoICAAQgAQQyQM6BggAEBYQHlAAWLkrYO5JaABwAHgAgAFoiAG_DpIBBDIzLjGYAQCgAQE&sclient=gws-wiz