Rega P25 w/orig Exact Cart - good? + mV question


Hi everyone, this is my first post and I'm getting the vinyl bug for some reason. So, I found a Rega P25 that has the original Rega Exact cartridge on it from 2001. The problem is that it's an estate situation and no one who is alive knows anything about the turntable, it's use, hours, etc. Obviously the remaining life on the cartridge would affect the value of the item.

How can I possibly tell if the cartridge still has a lot of life left on it or not? The turntable works, plays, and sounds great today and looks like it's been very well cared for.

And, what would you guys be willing to pay for a Rega P25 with an Exact cartridge on it, not knowing anything about the cartridge?

Also, I've been reading about different cartridges having different mV outputs, and so that raises another question. For now, this deck, if I buy it, would be going into a Yamaha RX-V3800 which has a 3.5mV input sensitivity spec and a 60mV maximum input voltage spec. Is this cartridge a good match for my receiver?

Thanks!
smhyde
There is a fellow on Audiocircle, 'Wayner' who makes a very nice set-up guide and protractor. It's made of laminated card stock and is quite inexpensive. It's far superior to the simple grid that comes with the TT. Check it out.
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You got a great deal, congrats. Just as a FYI - the acrylic platters are designed to be used without a mat.
@Viridian: I actually misstated a little. I don't have an Acromat. I have a Funk Acroplat Platter. The only mat I have for the glass platter is the ringmat. The original mat is gone.

@Slanski62 and Viridian: Thank you for the information on where to get a protractor.

@Goatwuss: You say the acrylic platters are designed to be used without a mat. How about the Acroplat Platter?

It looks like I have several options:

Glass with Ringmat
Acroplat Platter alone
Acrylic Platter alone

Does it make sense to also try the Acroplat Platter and the Acrylic platter with the Ringmat?

Finally, what exactly am I listening for when I try these different platters? Is the difference going to be obvious with casual listening or is this a difference I'm only going to pick up when listening to the same track of music on the different platters consecutively while sitting in the sweet spot at the ideal volume level and my ears freshly cleaned out?
Smhyde - at this point I wouldn't worry about it too much. Try a couple different things, just listen casually. If you can't easily tell the difference, just pick what looks best and focus your energy on cartridge setup. : )