DLB - They are indeed the same as the NA vans, for the most part.
A good reference for them is Toyotavantech.com (don't waste your time at TVP, hardly anyone goes there anymore)
TVT even has a subform just for those RHD vehicles and theres several members with them (and lots of info on them)
Seeing as they are quite similar to the NA variant, theres a treasure trove of info on that site, Tim, the forum owner has detailed many of his repairs, from engines to whatever you could want.
Its a great forum, almost as good as this one
From what I understand parts can be a pita but working on them isn't SO bad, mostly requires a perspective change, certainly harder than a turtle but not as bad as some newer vehicles.
As to doing the head, they can be done in situ.
There is a removable panel under the RS seat that, once out of the way, opens up the whole engine bay and makes access a breeze (once you've done it the first time, you can have it apart in about 15mins)
While the engine CAN come out from underneath, its actually easier to pull it out thru the RF door, you just need to keep the lifting chain choked up nice and short.
Taking it out from the bottom, you'll have to drop the exhaust, crossmember, front diff and propshaft, among other things, its pretty tight underneath.
Those vans do have a habit of eating heads, but once you get it all set up they are pretty solid, just don't expect much in the power department, the petrol versions actually have more oomph, in that respect.
That being said, at $600, you could easily make your money back just on parting it out, there are several guys out your way hunting for parts so you wouldn't have any trouble moving it, if it came down to it.
By the way, they are a blast to drive, the short wheelbase makes them infinitely easy to maneuver, and in 4WD they are a bit like a mountain goat, not too many places they can't go. Being "forward control" designed, the forward visibility is unrivalled.
And don't let anyone tell you they're a "death trap" in collisions, they actually fair very well in that respect.
I once saw a factory crash test vid where they drove it into a brick wall at 40mph, while it was dramatic (rear end bounced up a good 2ft) the front bumper was only slightly flattened without any visible body damage. Haven't been able to find the clip since but am sure its out there, somewhere.