Looks like the best turbo for your motor would be a Garrett T3 52 trim (link)
or a 60 trim T04E (link)
. I would go for the T04E because they are a lot cheaper, but you also get what you pay for.
I don't know about the 3800 blocks, but I got my oil feed next to the oil filter where an oil pressure sensor would be. I drilled and tapped my oil pan for a return line.
As far as tuning, I'm using a Megasquirt stand alone engine management computer. But that'* a lot of work. I don't know a whole lot about the 3800s but I would say grab the engine harness and computer from a series1 L67. Make sure you get the MAP sensor too.