Yes if you have another one to compare it to, otherwise you wont know what results you are supposed to see.

You can try checking resistance, but Simon seems to think that wont yield any gains, but you could also try checking voltage, Ive never needed to work out the pin configuration of a MAP sensor as I have always believed what the manufacturer tells me, but on for example a crank sensor if you put an osciliscope on it you can see the value changing when you pass metal pass it, so possibly you will get a similar effect if you vary the pressure going into the MAP sensor.

Ultimately one of the pins is going to change either voltage or resistance when it sees a change in pressure, so its a case of seeing how you identify that, which if you have a known configuration sensor in front of you, you can try looking for both resistance changes and voltage changes on that across the sensor pin in circuit with each of the other two pins to see what change occurs, then look for the same change on the sensor you have.

I personally would be talking to the manufacturer though, if they give you incorrect information in writing in an email that leads to you connecting 5v across it and that damages it, thats their liability IMHO in terms of replacing the sensor, but obviously I would be NOT using an ecu to supply the 5V I would be using a straight 5v dc supply to do so. (with a very low value fuse on it preferably to limit your chances of blowing the sensor)