Yeah, after draining the oil, basically you have to disassemble the whole high/low transfer case to get at it. Quite the PITA, but hardly impossible. No special tools needed. The high/low selector lever tends to freeze up over time, due to cooked oil in the vertical shaft that the lever connects to. Easy fix though--clean it out and coat the shaft with some high temp wheel bearing grease above the shaft's O-ring. Both of mine were this way; I have done one of them so far.
We never got the 110s with high/low, just the 90s. Our 110s had a normal front sprocket, like the newer CT125. Both of my front sprockets have some decent life left in 'em.
Link to my thread on The Carrot. Post #1 also contains a link to my other CT90, The Tomahto. Gonna get back into working on them this summer/fall.
https://www.chinariders.net/showthread.php?t=31919