One way would be to draw the basic cross-section of the Stargate parts which go all the way around and lathe it, then use that as a base upon which to add the other parts (the chevrons, the "egg-and-dart" panels between the chevrons, the glyph ring, the panels on the back side, and so forth).

I'm not sure how accurate this is, but here is my best guess at the cross-section. The line connecting the two parts is the "back" side of the gate, over which the back panels lie.

(I'm assuming Maya has a lathe function; my apologies if it doesn't and this advice is totally useless. I found this thread by following my Web site's referrer logs.)