Deciding the EV of a bet on the turn

[Nietzsche]

You hold 8/images/graemlins/spade.gif 7/images/graemlins/spade.gif on the button. The games is 6 max mid limits. Two limpers in front of you, SB (standard TAG 25/15/2.5) raises, BB folds, limpers call.

Flop comes K/images/graemlins/diamond.gif J/images/graemlins/spade.gif 2/images/graemlins/spade.gif
Preflop raiser bets, limpers fold, you raise, preflop limper calls. 6.5 big bets in the pot.

Turn is 5/images/graemlins/club.gif

The preflop raiser checks. Now the question is whether to take the free card or to bet. I think betting is often right because you will have a good deal of folding equity but this isn't the point of the post. What I am more interested in is a method for arriving at two numbers: The EV of betting and the EV of checking. How would you go about this? Or are there just too many factors to consider to arrive at two numbers that make sense. Of course precise numbers are impossible, but how about reasonable estimates?

Edit: Just to clarify I am only interested in Limit, not NL

It's very hard to figure stuff like this out. As long as you're a. not short stacked, and b. looking for the (non-nut) flush draw, you're not really making money on the raise this hand.

Regardless the EV of a particular play is very easy to calculate in one sense:
Simply multiply the likelyhood of every scenario by the net value of the scenario, and you can come up with your EV. What's hard is figuring out how likely the various scenarios are.