I'm a mechanic and have been in the trae for 15 year, Every clutch I do I usually take just the box out, Obviously I do them on a ramp at work but taking the engine AND box out will only give you more work in the long run, Never done an st170 yet but apart from the slightly larger 6 speed box it'll just be the same sort of setup as a 2.0 zetec.
Basically, battery and battery tray out, airbox and snorkle out, bottom balljoints out, drain box oil, both shafts out, gear linkage cables off, reverse switch plug, speedo drive plug, clamp the flexi hydraulic clutch pipe and disconnect the pipe from the top of the box, all but 1 front bell housing bolts out, starter bolts out but leave the starter simply pushed out the way aznd the cables still connected, trolley jack and block of wood across the engine sump, rear gearbox stabaliser mount off, 18mm gearbox top mount off, lower the engine and box about 4-5 inches to allow access to get the mounting off the top of the box (gives more room to lift the box past the inner wing), drop the trolley jack a touch more if needed, last bell housing bolt out and lift the box out with a mate as it'll be pretty heavy and a bit awkward
Hope that helps a bit mate
As per mr haynes "refit is reverse of removal LOL
While the box is off i'd check for any play in the dual mass flywheel