Hi Sean

I wrote that valve body service article about 3 years ago. There's an updated version of it at
http://www.volvoclubqld.org.au/index.php?option=com_content&task=view&id=58&Itemid=66

Anyway, I suppose you could swap the valve bodies but if it were me I'd like to know the condition of the replacement first. If you can drive the car and all seems well than it might worth a shot. If the transmissions are the same (eg. both AW70) then the valve bodies should be too. Anybody feel free to correct me on this.

The valve body is a self-contained unit. All the little parts are inside and if you don't pull it apart there won't be any problems.

To get it out unhook the kickdown cable, undo all the bolts (there are different lengths in different places so make sure you devise some way of remembering where they go. See this pic

http://www.volvoclubqld.org.au/images/stories/documents/valvebodybolts.jpg

I'd also strongly advise making up a retainer plate to hold the accumulator pistons in place when then valve body is removed.
When it's out then you can chuck in the replacement.

But like I said, you'd want to be sure the replacement is better than the current one otherwise you're wasting your time and money. The service isn't all that hard but you do have be very careful, methodical and scrupulously clean. I did it in a weekend but I was taking my time with taking pics and all.

Hope this helps.
Brad
91 940GL