I just replaced the tank and regulator on my 1984 Westfalia. The tank is heavy and clumsy, but is straight forward. (See post in tank.) All the trouble really lies in the lines.
On the GoWesty website, they explain that the current regulator is different than the original one and that you have to cut and reflare the copper lines. What they DON'T explain is that new regulator sits up almost an inch higher than the original one. At least this is true on a new tank and new regulator combination.
Reflaring is not fun, but with a flaring tool and pipe cutter, it's only about 30 minutes of work. I recommend getting the mini pipe cutter. Swinging room is very tight. However, after measuring and cutting 1.75 inches from the lines and reflaring them, the lines didn't match up at all. And because it is heavy duty copper pipe and you are dealing with a relatively small amount, thus reducing your leverage, there is a limit to how much you can bend it.
Here's how I did it:
First, remove the skid plate. I spent 30 minutes goofing around with it in place and eventually I had to remove it anyway.
Second, go into the under sink cabinet. The gas lines run up through it to the stove and fridge. Empty the cabinet and loosen the clamps that hold the gas lines to the cabinet. In my case, I had to remove both shelves to get access to the Philips screws. Then pull the lines up as much as you can. There is a lot more room for flexibility in the lines at the top than the bottom.
Third, don't tighten the regulator to the tank. You need wiggle room in the lines. It is the classic, "attach but don't tighten." I forgot that, of course, because I was so concerned that I have no gas leaks, so it took me 45 minutes of pushing and grunting before I remembered the basics of any kind of plumbing connections. You still have to bend the lines, but by having more wiggle room it won't be as extreme.
Fourth, attach both lines, but just enough to know the threads are on there straight. Then, depending on what kind of "Y" fitting you have, use a regular or pipe wrench on the "Y" connection and tighten the flare fittings to the "Y."
Finally, tighten up the regulator to the tank.
Also, remember that the tank was of U.S. manufacturer and all the nuts are based on the inch system, not metric. On my vehicle the flare nuts were 13/16 and the regulator was 7/8. Make sure you have real wrenches in the correct sizes. There is not enough room for an adjustable (Crescent) wrench.