[Stiglr]

I would suggest cutting the windows. Not knowing your aircraft, or having a screengrab to go from, I'll try and wing it (bad pun, I know) and offer some general advice:

If there are some surfaces that roughly describe the window area (and, if you're modeling the exterior, I'm sure there are), perhaps you can simply "cut away" those surfaces into separate objects and assign them a material that's 95% or so translucent. Depending on the level of detail you want inside the cockpit, you may or may not need to indent them to create framing around them... you'll perhaps want some photos or detailed plans of the helo to work from to help you craft the interior.

As for the interior itself... it's really little different a process than creating the exterior. To start with, make a copy of the main body, hide the rest of the model and paste the copied body. With the entire part selected, and in surface mode, make the object 1-sided. Reverse all the faces so that they face inward. Go to object mode, and scale in all three dimensions to 98 or 99%, so that the surfaces of the exterior and interior bodies don't occupy the exact same space (and "visually vibrate" as a result). Voila, you've got your interior cabin.

After that, when I'm creating aircraft, I will then look at the interior and identify bulkheads and panel lines/rivet lines that "jut into" the cockpit. I'll use rectangles and the Knife tool to "describe them" and then extrude them into the cockpit to create the "framework". AC3D now has a great "Extrude by distance" feature which keeps you from having to move various areas of the framework separately. You can often grab an entire framework that goes all around the cabin and extrude it all at once. Only if, for example, the horizontal frames are not the same depth as the vertical framing, will you have to do more work to create that look.

I'll often have to "seal off the pit" by finding where the bulkheads are, but with a helicopter, the nose is likely the front of the cockpit... so you may only have the rear bulkhead to consider. Personally, getting the "edges" right: the bulkheads, the canopy coaming, any window opening/closing apparatus to be the hardest parts to get perfect, and are often the sources of the most frustration at doing properly. But stick with it, and use photos as your guide and eventually, you'll get it.

After that, it's a matter of creating the gear inside the cockpit. Again, because you won't usually find "3-views" of interiors, you'll have to rely on photos or diagrams and create objects using primitives: cylinders for the collective control and for pedals... polygons for panels, disks for gauges; boxes for seats, switches and internal panels and mounts. The same way you used a box or a cylinder to create the aircraft body. Same concept.

One thing that helps: if you have an illustrated flight manual or repair guide that has a good, clear, straight-on view of any control panel... it is sometimes helpful to get a scan or graphic of the panel, use it to texture a rectangle in your workspace, and then "trace" it to create an accurately shaped polygon. Then, if you know the radius or dimensions of any gauge on the panel, you can create disks of the same radius to use as a scaling guide to accurately size the whole panel... then extrude it a little to get some thickness... and drag it into position in the cockpit.