PokerStars No-Limit Hold'em, $0.05 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

BB ($10.72)
UTG ($5.65)
UTG+1 ($6.93)
MP1 ($2.08)
MP2 ($5.25)
Hero ($4.93)
CO ($4.43)
Button ($6.92)
SB ($6.09)

Preflop: Hero is MP3 with K, K.
2 folds, MP1 calls $0.05, 1 fold, Hero raises to $0.25, 4 folds, MP1 raises to $0.75, Hero ???

After grinding some 11,000 hands at 2NL ($25.00 deposit), I finally got the 20 BIs necessary to "take a shot" at 5NL (as lame as it sounds). So this is my first time at 5NL which I single-table.

This is like the 4th orbit. Read on MP1: limps premium (KK, AK) in EP.

Should I push with the attitude "if he's got AA, he's got AA" or should I flat-call and put the money in on the flop if there is no A on the flop? Or is either fine?