The dip switches changed are in the Amptron PM-9800 manual as from the d8b resource site somewhere, but here's a basic explanation:
With the cover open and the front of the unit towards you, there are three groups of 3-gang dips near the bottom edge of the board. There are NO other dip switches on this board. (you have more? wrong board. Stop.)
The RIGHTmost is 1, then middle is 2, and LEFTmost is 3. On sw1, the dips are all 0, or down. On sw2, the 166 settings are 110, but with the 233, this is now 100. (1=on) This one is the core voltage setting and the 233 operates at a lower voltage.. don't screw this one up. On sw 3, for the 166 it's 110, and with the 233, change to 000. (all off, like sw1).
The 166mhz ceramic is model P54C, the 233mhz is P55C. Ensure you have some heatsink compound (can be scraped from the previous chip if it was anything like mine..) on the metal centre lid, though this OS isn't CPU hungry (unlike ms-win) most of the time. (That was impressive by the way; The cpu was as cool as the metal case when running for a while.. no temperature increase. This would indicate an efficient OS...)
There's a picture of the manual, with my notes as I did my board.
And please exercise caution; double-check everything before powering up afterwards.