does anyone know how reclassing to an 18 series MOS works? would you go through 11b AIT before selection? any info would be helpful

You won't re-enlist I don't think until after you completed SFAS and the Q course. I have had plenty of friends do this and they don't re-up for it.

But no, you don't have to go through 11B AIT before selection.

You volunteer for the whole shebang prior to getting a class date for SFAS; you demonstrate fitness at SOCOM standards (typically the 17-21 270 level), you complete the volunteer 4187 for Airborne training (which stands regardless of the outcome for SFAS or 18 series, BTW), and you undergo an Airborne physical (also on record from then on). You go thru SFAS, if they accept you (which is different from meeting any particular published standard), you get a return class date for the Q course, which awards you the 18CMF upon graduation. THEN you go to specialization course which qualifies you for a particular 18 series MOS. You'll get the 11B training somewhere in there, but until you're graduated from your specialization course you're whatever MOS you were when you signed the original 4187 for jump school.
Keep yer head down, drive on, and be ready for whatever.