AHS has what's supposed to be a good extract kit, but I have no idea what's in it. The following is what I'd do to take a stab at rolling my own Oktoberfest extract recipe:
Generally, pilsner malt + Munich malt + Vienna malt = Oktoberfest. I'm not aware of any Vienna extracts but they do make Munich extract that is generally somewhere from 30%-40% Munich Malt and then filled in with Pilsner. You could probably get by without the Vienna by steeping some CaraMunich. That'll add a little of the missing Vienna's roastiness back. If it were me, I'd try:
4lbs Munich LME (assuming a 40% Munich mix)
3lbs Pilsner LME (EDIT: typo corrected)
1lb Caramunich steeped
and then grab a hop profile off a decent Marzen all grain recipe. According to BeerSmith, that still gets you in range color-wise and is as close as you're probably going to get to the actual typical grain ratios.
Like I said earlier, that's just a stab at it based off of my own experience making Marzens and based on how extracts I've never used should behave. Prepare for at least a little trial and error.