5CD - bluff or not?

[THEjDonk]

Right now I don't have the tournament history for the latest tourney I played. Should I strive to produce hand histories from 5CD? If so, can you tell me about a good converter that's compatible with Pokerstars?

Here's the main question:

This is in the latter stages of the $5 limit 5CD MTT on Pokerstars today. 16 guys left, 8 get in the money.

Villian limps in from an early position. I have pocket aces in the small blind and raise. Only villian calls. Both draw 3 cards. Now the pot contains 3000 chips, and my opponent bets (1200 chips). I have 1600 left and didn't improve my aces. I haven't seen my opponent making a whole lot of bluffs. but he's also shortstacked and almost all-in. Perhaps he's figured me for aces and tries to bluff in an attempt to get himself a "real" stack.

I don't have a very good read on my opponent, so I have no idea how often he has a smaller pair here.

Is it ridiculous to fold aces here, or is it very likely that my opponent has me beat? If I fold this hand, I'll have less than 3 BB left. That means that I might be forced to "push it in" as an underdog pretty soon anyway.

How often would you say that I have to be ahead to call here, and how often do you think I'm ahead against a typical (limp-with-a-pair-) opponent?