When to let go of overpair $50+5 lvl 1

[elena_elphie]

I'm unclear on how willing I should be to go to the felt with an overpair against a typical opponent at the 50+5 level. If opp shows any signs of donkiness I am nearly always willing to, but this is hand 3 of a tournament against an unknown, so no reads, except villian raised preflop hand 1, bet on flop and folded to a raise:

Party Poker No-Limit Hold'em Tourney, Big Blind is t15 (10 handed) converter

Button (t1075)
SB (t870)
BB (t970)
Hero (t1000)
UTG+1 (t1000)
UTG+2 (t1000)
MP1 (t970)
MP2 (t885)
MP3 (t970)
CO (t1260)

Preflop: Hero is UTG with A[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">Hero raises to t45</font>, <font color="#666666">3 folds</font>, MP2 calls t45, <font color="#666666">5 folds</font>.

Flop: (t112.50) J[img]/images/graemlins/club.gif[/img], 8[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets t75</font>, MP2 calls t75.

Turn: (t262.50) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets t180</font>, MP2 calls t180.

River: (t622.50) K[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, MP2 is allin, Hero folds.

Final Pot: t622.50

What should I have done on the river? Should I have done anything differently. I felt I was put in a tough spot by villian's allin.