Does your current steering wheel have an airbag? If it does then there's a good chance that it's illegal to replace it with a non-airbag steering wheel. Be sure to check with local authorities first. To remove one with an airbag you will need a Torx socket to remove the airbag assembly and you'll need to disconnect the negative cable of the battery for at least 5-minutes before attempting removal.
If your current one is a non-airbag steering wheel then the removal is a lot more straight forward and there's no need to disconnect the battery. Start by removing the Philips head screw underneath the steering wheel. This will allow the hornpad cover to pop off. Disconnect the horn connector and you'll see a large 19mm nut in the centre of the steering wheel. Loosen this nut until it's almost at the end of the thread. Now put both hands on each side of the steering wheel (in about the 10 o'clock and 2 o'clock positions) and rock it back and forward, side by side. This will cause the steering wheel to become loose, allowing you to remove it from the steering column once you remove the centre nut completely. Failure to leave the centre nut partially on the thread will likely result in you being smacked in the face and left with a black eye. If you're having real trouble getting the wheel free, pop down to your local auto store and buy or rent a steering wheel puller - It will make your life a lot easier.
If you're swapping to an aftermarket steering wheel (such as a Momo), try and find one that's as close to the stock steering wheel size as possible. This way you'll still have an unobstructed view of the instrument cluster. Most aftermarket steering wheels are considerably small than the OEM wheel, so you have to peek underneath it sometimes to see what speed you are doing. Bear in mind that you'll also need to use a boss kit with any aftermarket steering wheel, and they are vehicle specific (so make sure it's compatible with Toyotas). Swapping the steering wheel is definitely a worthwhile upgrade as they often not only look better, but feel better too, due to the increased grip over the stock wheel. Just be sure to check to see if it's legal in your state before spending a cent