I've never done the water pump on a new-ish sedan. I imagine it would be a cast-iron bitch to get to, though. Same with the A/C - mine made noise like you describe, and it turned out the compressor clutch was shot. When the technician removed the compressor to inspect it, there was a lot of internal wear, so I went on eBay, bought a new compressor (w/ clutch), and had the tech install it. I do a lot of work on my cars, but the engine on this thing is beyond the time and effort (and tools) that I have available.
Your best bet would be to try confirming it's the water pump, then buy the part on eBay and hire a shop mechanic to put it on for you. If you go to Firestone or the dealership they'll take you for every penny, and make you use their parts at a huge markup. A local auto shop probably won't mind using 3rd party parts, and will charge a fair rate for labor.
Corsair (noun) - a privateer or pirate
"Wicked": 87 Olds Cutlass Cruiser Wagon - totaled in blizzard
"Beast": 89 Buick Century Custom - totaled in driving sleet
"Cutty Sark": 97 Olds Cutlass Supreme - died too early
"Batmobile": 98 Cadillac Eldorado Touring Coupe - ditto
"Grey Ghost": 02 Infiniti I35 Sport - still ticking, needs new water pump
"Red Devil": 08 Pontiac G6 GXP - current ride
"My Boy Blue": 00 Ford Ranger XLT Club Cab - my hauler