EC 200 set-up tips needed

[bondo]

Just picked up an '05 EC 200 for my teenage son (apologies to Boomhauer).
i ride orange and was initially looking for same for him, but the more research
I did, the better the GG bikes looked. We finally found the '05 just a few miles from home. This is our first Gas Gas so I could use any advice about setting up the bike for a long, happy life in the tight woods.

This particular bike seems to have fairly low hours on it and mostly needs just a little TLC to sharpen it up. First question, what about the forks? The previous owner has the Ohlins units mounted, but has a set of 'zokes in a box.
I'm well aware of the reputation both units have, but have never ridden either.
He's willing to include either set (but not both, darnit!). I'm planning on trying them both, but could use some input, especially as relates to tunability and
performance in the tight stuff.

Also, what about the spring loaded chain guide on the swingarm?
Should we keep it or replace it with a more traditional block style unit?

Finally, the sag on the rear shock. I was accustomed to running about 90mm of sag on my Ohlins equipped KTM for the riding we do and was planning on starting there for this bike. Comments?

As I said, we ride mostly tight woods. Plenty of rocks, ruts roots etc . . . Lots of elevation change.
If the trail opens up enough to use 4th gear, it's considered a fast section
(for me, anyway), but mostly 2nd and 3rd gear sections.

Any comments or advice about setting up and maintaining this bike would be most welcome.