One other trick with the return line...
set the turbo in place and try to start the bolts. You'll notice the return line needs to be moved one way or the other to line up...
remove the turbo and tweak the line a little. What you're shooting for is for the return line to be lined up with the turbo while it's in it's happy place. That way you only need two hands to start the bolts.
Also, make sure the flange is flat. It's very easy to bend, and fortunately very easy to bend back. a couple pair of small vice grips with dull jaws make easy work out of it. I like to leave a slight convex surface to it that way the bolts get to pull it down.
A thin smear of RTV on the flange, both sides of the gasket and the housing will fend off any leaks. Let the RTV 'skin over' almost to the point of being dry, then lock it down (just like on headers, only with a gasket)