Battery dies without warning

Hello I realize there are other threads about this on this site but none of them seem to pertain to my particular problem. Today I was using my macbook doing nothing too intensive (internet browsing between two tabs), and my computer shut down without warning. My first instinct was to turn it back on, which I did. The power came back on for about 10 seconds, just long enough to show the white screen, and shut off again. I then plugged in the ac adaptor in and the computer turned on fine. Upon logging in the battery status indicator at the top right said my battery was at 8%. Other times when my battery was at 10% I got the standard message telling me to connect to AC power, and it always runs down to 1% before putting itself to sleep. When I would plug in the charger the computer would wake uo from sleep without any work lost, but this time was completely different. As I said, with absolutely no warning, the computer turned OFF.

I have recently reset the SMC and PRAM to help combat bizarre fan speeds and it seems to have worked. I don't know enough about macs to know if this had anything to due with the warning not appearing.

Under System Proflier > Power, this is the data:

Battery Information:

Model Information:

Serial Number: SMP-bq20z451-3ad7-3155

Manufacturer: SMP

Device name: bq20z451

Pack Lot Code: 0000

PCB Lot Code: 0000

Firmware Version: 0003

Hardware Revision: 0002

Cell Revision: 0100

Charge Information:

Charge remaining (mAh): 1339

Fully charged: No

Charging: Yes

Full charge capacity (mAh): 4248

Health Information:

Cycle count: 317

Condition: Good

Battery Installed: Yes

Amperage (mA): 3194

Voltage (mV): 12025

I have had this computer for 3 1/2 years (July 2009) and it is not currently under any type of warranty. Is there anything I can do about this or should I just fork over the cash to take it into an Apple Store?