This was one of the more complicated hands I've played in a while, and I'm still not sure what to do.

I didn't have very many reads, but I've seen UTG before and get the impression that she's not a horrendous player.

Paradise Poker No-Limit Hold'em, $1 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($41.00)
Hero ($194.65)
UTG ($108.50)
MP ($1696.70)
Button ($343.15)

Preflop: Hero is BB with 6, 8. SB posts a blind of $1.
UTG calls $2, MP raises to $6, Button calls $6, SB (poster) calls $5, Hero calls $4, UTG calls $4.

Flop: ($30) 5, 5, 7 (5 players)
SB checks, Hero checks, UTG checks, MP bets $30, Button folds, SB raises to $35, ($35)UTG raises to $137.5, MP calls $72.50, Hero calls $67.50.

Turn: ($337.50) A (4 players)
Hero checks, MP checks.

River: ($337.50) 8 (4 players)
Hero checks, MP checks.

Final Pot: $337.50