Knew I should've posted about this when I had the prob!!
When I bought my Lag II, the rear wiper was also siezed. Motor was fine, but mech was stiffer than, er, a stiff thing...
In the end, I had to replace everything connected to the glass. Why?
1) Needed a new blade anyway!!
2) arm broke when removed from spindle - the arm was slightly corroded, as was the spindle, and the corrosion had welded them together
3) spindle mechanism stiffer than a stiff thing... also had part of wiper arm welded to it!
4) the nut against-ish the glass had also seized to the spindle mechanism. No amount of WD40 would free it. In the end a socket set with a very long handle loosened it... I thought, until I looked!! Snapped the thread!!
At least now though the whole lot came off the glass nicely!!
Cost me about £100 to replace the lot - plastic caps and all.
Greased it all up with copper grease when I refitted it to help prevent corrosion and further siezure.
Trouble is, I now need to strip it all down again to tighten the bolt against the glass!! Hope the arm doesn't break again!
Oh, if you're really stuck on how it all comes apart, I *may* still have the print out the parts desk gave me... or it may have been filed under "B" the last time I cleared my car out...