You cannot do either.
There are no inter service transfers from the Marines to the Army
Although Marines can apply for Delta/CAG
The 18x program is for new accessions only.
You would have to finish your Marine enlistment, then enlist in the Army.
Then apply for SFAS.
But you would be able to apply for and go to SFAS pretty much as soon as you were assigned to a unit, but they will make you have 12 months time on station, before you can can attend SFQC.