gbs you have a PM
I've done a ZX TD recently, which is the same box / clutch as the Xantia. Not too bad - but much easier with 2 of you and some sort of overhead lift. The box is not that heavy, so doesn't need excessive slinging. If you take a rope from the lug near the starter to the one near the gear change input, this will give you the correct rotation of the box. Add another sling from the lug at the outboard end of the box and this will support it in the correct angle to get the input shaft in. I was fretting about getting the box back on with the pull clutch, but it went second time after we twiddled the input shaft to get the splines lined up with the friction plate. Haynes doesn't make a particulary good job of describing it, but once you get into it, it's obvious, and there's enough room to see / get your hand in to get the fingers on the fork lined up. It's a good idea to completely remove the speedo drive housing as this makes it easier to get the box out past the flywheel. Other than that it's just the ball ache of stripping everything out to get the box off.