I would only replace it with an OEM clutch unless you're upgrading the transmission too. Usually the clutch will slip, so change in pedal feel is a little abnormal. Like you said, sounds like a hydrolic problem .. or it could be a mechanical issue with the clutch itself. As long as it isn't the transmission you shouldn't be too bad off. The flywheel should be replaced along with the clutch. As far as cost, that's going to depend on who does the work. It wouldn't be out of line to expect to pay $1200 to replace it, although I have had shops charge as little as $300 in labor when I brought them the parts. Clutch install isn't that difficult.
The price of the car seems a little high to me. Remember you're talking about a ten year old car with 130k miles. It's at that point in its life where it is no longer going to be trouble free. It wouldn't be surprising to have A/C, alternator, or other problems. My 02 has 120k miles and I recently had an alternator crap out, and my A/C compressor sounds like it's on its way out as well. I'm also beginning to have slight electrical problems, like my dash lights flickering off and on when I go over bumps. These are things to be expected with an older car.
I would look at the blue book value, subtract the cost of the repairs you are going to need, and see how that number lines up with the asking price. If the car has been well maintained and you don't beat it to death it could last for a long time, and in the end it's up to you whether it's worth the money or not.