Don't need to take the wheel off...unless 'rear linkage' includes wheel bearings. Well, and/or swingarm stuff.
Put the thing on a stand so the rear wheel is just touching. Take off the 'stuff'. Clean it. Pack new grease in. Put it back together.
A bit more on 'stuff': You will want to remove the unitrack arm altogether for easier access. It attaches at three points..the swingarm, the frame and the shock. The swingarm connection is thru the pull rods.
Don't bother with the top shock mount. There isn't a bearing there to mess with.
When it comes to reassy, make sure the pull rod bolt shoulders are thru the pull rod. They are kind'a short......it's easy to tighten the pull rod against the shoulder of the bolt especially with the seals full of grease.
It will tighten up to spec. Then the first time you ride it, it will dislodge from the shoulder edge and the linkage will be slopping around, wallering out the pull rods and damaging the bolt shoulder in the process.
Getting to the swing arm bearings is easier with the wheel off. Just take it off, save some time.
Use the best grease you can get. Your basic one-each moly-di-sul chassis grease won't do the job. A good waterproof marine application bearing grease is probably ok. I use some super-d-duper stuff given to me by my riding buddy..hydotex parasyn 70. It's the only grease I've used that keeps the bottom shock mount bearing good from one grease job to the next. No, I've not tried dozens of types..but several. It's purple (ain't it purty?) to boot! (get it..purple? super-d-duper? Thassa joke, son!)
No, no special tools required.
Torque to spec on reassy!