I wouldn't marinade defrosting meat- the juices which come out need to be dumped, and if you marinade thawing meat they really dilute the marinade and make it less effective. I'd defrost first, and cut it up before marinading.
As for how to cut it up- take off any fat, and slice it into nice strips. Discard any stringy bits too.
amandaelizabeth is absolutely right- long and slow or hot and fast. If you do cook it fast it should still be slightly pinkish in the middle.
It is absolutely delicious.