You can't use a Cat5 cable longer than 350 feet. Wireless typically only reaches 300 feet, with very poor reception at the last couple dozen feet.
If you want to attain 1Gbps speeds on your network you'll need a Gigabit card at all machines you wish to reach gigabit speeds at. Combining a Gigabit card in one machine with regular 10/100 cards on other machines will result in only reaching 100Mbps speeds. Typically these Gigabit cards are much more expensive than a regular 10/100 ethernet card. Also the cabling needs to be seriously good cable to reach maximum speed. Inferior cabling will interfere with the signal, resulting in reaching less than gigabit speeds.