As for servicing my shock, is this something I can or should do myself, or should I send it away?
Again no expert here, just like to work on stuff.
No, you can't do yourself. Need more equipment. Vacuum, Nitrogen, etc.
Could but would have to but bunch of stuff, maybe $300-$400 worth
If you send out they can also dyno the shock and look for any problems.
Also, bladders have been known to leak and might need repairing.
Also, since I'm at that service interval, should I start thinking about servicing my forks too?
Yes, I might be a little different then others, but I change fork oil on all my
bikes every 12-18 months.
I also like to experiment with slightly different oils weights and fill heights.