Internal leak in brake actuator

2005 Prius, around 190,000 miles

For a few weeks now I've heard the "buzzing" under the steering column get more and more frequent. Every once and awhile in the last week I heard some kind of alarm when starting up, but couldn't nail down what it was. Today I finally got the red BRAKE light, the yellow brake warning light, and the ABS light. I took it to the dealer who pulled the following codes (I pulled the descriptions from the repair manual):

• C1241 - Low battery positive voltage or abnormally high battery positive voltage
• C1256 - Accumulator low pressure malfunction
• C1391 - Abnormal leak of ACC PRESS

All the dealer said was that there was a leak inside the brake actuator and would cost $2718 to replace (he did not mention an issue with the battery). He said this problem would only affect the ABS, and that I still had brakes.

Has anyone dealt with these codes before? I just wanted to get the community's opinion on this before I pull the trigger on such a large bill.