Just draining the crankcase and re-filling it with Mobil 1, 0W40 will be fine. No need for a flush with oil or anything else. If you wanted to, a change interval of 2500 miles for the second oil change might rid the crankcase of the old oil sooner but it's certainly not absolutely necessary. The majority of the new oil will be Mobil 1 with just one change. JK
After I did this the first time and found out what a freakin hassle and mess it was trying to work around that brace, I picked up a Pela 650 extractor.
Works just fine.
I will probably pull the drain plug again a few changes down the road just to make sure everything's kosher, but if you're running a good synthetic (especially if you've had a flush) it should be no problem.
The oil filter still makes a mess though, been thinking about installing a relocator kit for it.