What can I expect from the 18D course?

You should focus on passing SFAS first. You might not even receive 18D as an MOS. When I was selected, I was a 68W and I received the MOS 18E. It's about what the Regiment needs, not what you want.
You won't find accurate information on the specifics of the course because it's constantly being rearranged.

Right now, I suggest you focus on the steak and not the peas. Get into Selection and pass that first. Everything else will fall into place.

You should be focused on making it through selection first. IF you are selected to attend the Q course you will then have to fill out a wish list where you rank your preferred MOS (18B, 18C, 18D, 18E), preferred group, and preferred language. A board then assigns your MOS, group, and language based upon the needs of Special Forces at that time, though most are able to get the MOS they desire.

Good stuff. Please swing by the SF Recruiting Station at Ft. Bragg and get the latest and greatest from the SME

‭ BLDG C-5437 Bastogne Rd.
Fort Bragg, NC 28310

Go to the SORB on Bragg. There are a few SF guys there who can break it all down, if there isn't a Medic, they can get you in touch with one. Their job as SORB Recruiters are to explain everything like the questions you have about Q course and everything else. While you have gotten some info here, no one is in CMF 18, so it's all what they've heard and learned throughout their time (no offense SFC Thomas Livingston), and they aren't wrong in concentrating on SFAS first.
I could go into the whole thing as I hear the SF brief on a more than weekly basis and even conduct the brief from time to time, but your best bet to get ALL the answers you seek is to go down Ardennes (the S is SILENT!!!) and right next to SRP and the Airborne Lanes is the old bank which is now the Bragg SORB, walk in the door on the right and talk to one, or both, of the Green Beanies there. They can handle everything.
Goarmysof.com

Hello,

Prior to MOS selection you will have to go to selection and get selected before the SF considers you to go to Q course. You also have to be airborne or volunteer for the airborne school. Prior to q course, but ultimately it depends on your status if your guard, active, or reserves. Process is different for all

First learn to spell. You will have to learn Doctor Level Medicine while maintaining excellent physical shape. Errors get people killed even in peacetime in that job.

So from what I have gathered from your comments you are focused on the Q course. What these good NCOs are telling you is to be focused on Selection which comes before the Q course. Which is solid advice as passing SFAS is a feat in and of itself. But for 18D you’d be looking at a longer pipeline than than other 18 series. As a 68W I don’t know if you’d be able to test out or skip some of that. But you’d spend time outside of Bragg learning the medical portion before going to the qual course is memory serves

To clarify I am very focused on the q course above anything else. I just want to be sure I know what I'm signing up for. Everything I have read is vague.