How can I extend DSL wireless signal to outbuilding approx. 75 ft. away. I have a Cisco E3000 Wirelss router?

For such a short distance you really don't require a repeater, simply a better antenna. Yagi antennas concentrate the signal to a particular direction (hence they are called directional antennas), thereby making the most efficient use of the available signal. An easy way to accomplish this is to build your own, they are quite simple and numerous sources are available with step by step directions (one of which I've attached to this answer).