reservoir container filled with dark liquid

That container is your brake fluid. It needs to be changed.

 

Toyota USA says it's lifetime, I guess. Well actually, they say nothing.
Toyota Canada, just in the last few years, says to change it tri-yearly or 30K miles (48K kms).
Honda Canada, for as long as I can remember, says change it tri-yearly, regardless of mileage.

The 3rd gen offical Repair Manual has an instruction, for brake fluid change without Techstream, and is relatively easy to DIY. 2nd gen I haven't found anything comparable, and I'd suspect it's best to check dealership service department for this. Try to verify they've experience at it...

FWIW, here's a second gen brake bleed instruction from the Repair Manual, using techstream:

 

Look in your service book for brake fluid inspection and service. If your car is older and this is the original fluid, fluid replacement might be in order. Brake fluid attracts moisture, thus the replacement interval.

Edit - I don't see a service interval for brake fluid in the US manual. Just a check/inspect with no criteria for failure. If the brake fluid is very dark (as opposed to the somewhat dark of fresh fluid), it would not be unwise to change it.

 

The spokesman for Bosch Brakes that spoke at the seminar I attended for my work actually recommended a 24 month change interval for brake fluid, and discarding any fluid that had been unsealed more then 6 months ago.

 

It'll be 3 years this fall since my last DIY change, will do it agin, while swapping over to snow tires. I'm sure you can do it without wheel removal, but it's not as accessible. Kudos to @NutzAboutBolts for blazing the way, btw.

Again, haven't seen a second gen DIY.

 

Brake fluid which appears to be pretty dirty. Better have it flushed.