new 78 300D owner....; help!

[deferr]

i just bought a 78 300D that had sat in a garage for 4-5 years being driven a couple times a year. I thought i should flush the fluids and replace them since they were probably pretty old. I bled the brake lines and the brake fluid was very dark colored. I test drove it and noticed the brake light is now on, however my braking ability has improved substantially since i bled the lines. Any help with this problem would be great. Also the transmission fluid is murky in color..... does this indicate it needs to be changed and if so is that something i could do myself????