I did a spark plug change at 60k, following the usual pdf guide and thought I'd share some tips.
Remember to disconnect the battery first. Note that doing so will cause a self check on the next start up and clear your MPG records. The first start also takes ~ 0.5 seconds longer, so hold the start button down else it may stall and you'll panic!
The 5mm allen key you need has to be a long thin one, multi-tools & socket sets are no use here. Don't get the useless ones with a ball on the end. Use a pair of pliers / mole grips to gain leverage if necessary. The one closest to the firewall is the most difficult of all, so do that first, then the one in the centre so that they are under the least load (less torque to undo them).
Have a nice strong magnet (old hard drives are great for these, or speakers) to hand to help draw bolts out (attach to screwdriver) so you don't drop them. Get some spare engine cover clips, plastic ages, and after 60k and several years in a hot engine bay you'll find some don't secure like they should. You also stand some chance of losing / breaking some if you don't have spares.
A 10mm ring spanner is essential for removing the bolt on the side of the throttle body unless you want to be frustrated (sockets won't reach). Also make sure you have a good 10mm socket and 10mm long socket, same goes for 12mm. Always make sure you know which way loosens and which way tightens when working in awkward places.
Removing the battery and the case completely it's in might seem fiddly, but the improved access to the bolt at the rear of the intake manifold makes it well worth your time. I've seen people report difficulty fitting that nut back, so even if you can get it out, don't anticipate getting it back in with the battery in place unless you have small hands and a lot of luck.
The spark plugs are down a deep (20 cm?) hole, so your socket extension needs to be long enough for the job. 16mm magnetic spark plug socket is what I'd recommend. I use a Sealey AK654 as my torque wrench is 3/8" drive and recommend you get a name brand one rather than a Chinese no-name brand. Remember to put aside the wrench and use your fingers for everything but the loosening and final tightening - this helps to avoid cross threading. Play around with a new spark plug and the socket before you start work and you'll get a sense of how it fits together and how things should feel (since you can't see it in situ).
The large jubilee clip on the air intake hose may need some jiggling to relax its grip once you have loosened it. You can tap the clip itself or wiggle the intake hose around. It won't take much force, but may take some patience if it's grimy.
The passenger side rearmost spark plug has something grounded kind of in the way, loosen that to rotate it out of your way, it's torqued down very tight from the factory, so make sure it's gud'n'tite when you tighten it back up as well.
The spark plug connector is easiest to loosen using a fine flat screwdriver rather than your thumb. Insert from the spark plug side (not the wire side) under the catch and gently release it by lifting that side up a mm.
Undoing the 10mm nuts holding the plastic wire housing which routes to the spark plugs makes access much easier. Even if it's not obviously necessary. It's obvious how it goes back on, and you're not going to cross-wire your plugs without effort.
What might you forget to do back up? The jubilee clip on the air intake; the clips which secure the vacumn hoses to the intake manifold; the bolt at the back that secures the intake manifold to the engine block; the nuts on the battery; the hose holders which help with routing and secure hoses to the intake manifold / air intake; the wire which connects to the air intake; the battery sensor on the side of the battery case.
Overall the job is very easy if you use those tips. With a relaxed pace this is easy to complete with the right tools on a cold (never hot engine!) in about 1.5 to 2 hours even with little experience. If you take lots of photos and triple check everything you'll still get it completed inside an afternoon.
Since you'll have access to the intake air filter, give that a visual inspection / clean / replacement at the same time. It's a ten minute job to get at it normally (due to the plastic engine covers), but 0 minutes extra in this case.