I've been modifying the seal head to take a readily available Showa seal. The original WP seals are very hard to get.
The bush housing will be stupidly tight. Make your tool carefully!
Running boiling water over the shock body, and then some WD40 (for the coldness as much as the lube) on the bush housing will help.
For bleeding, I've been drilling and tapping the banjo bolt on the shock body, to create a bleed point. Seems to work fine.
Pretty sure that 7.5W is right (will confirm later). Exact volume is determined by the height of the floating piston in the reservoir. A 1litre bottle is enough.
Also be aware of the holes in the shims - they've gotta line up with the holes in the piston. Its really obvious once you think about it, but could bring you undone if you don't think to look.