I just did 9 gallons of a vienna lager which is pretty close to a marzen. 100% vienna weyermann. combo of hallertau and warrior to bitter and a pinch of hallertau at 10. 25ibus. saflager 34/70.
I prefer my oktoberfests on the maltier side, so id probably sub 20%+- of munich and get the OG in the 1.052-1.055 range. use weyermann or a continental malt. probably go with a nice liquid yeast, german or marzen if you can too.
mine is 2.5 weeks in, first sample yesterday tasted nice, its done fermenting and has been raised to 62 for 2 days. letting it go to 65 for another day or 2 just to make sure no diacetyl. crashing, kegging then letting it sit for 6-8 weeks to lager.
i know that doesnt help a whole lot but hope it gets some ideas marinating in the ol noodle for you.