Matlab Drawing: signal freq analysis

I'm new to matlab and signal processing issues, but I'm in need to answer the following questions to complete a project that depends on them.

suppose I have a grid where x-axis implements time, where as y-axis implements the amplitude. Knowing that sampling rate = 256. Based on the input signal:

1) How would I know the average frequency of that signal (knowing that it might not be a uniform signal)?

2) How would I represent/draw the "fast Fourier transform (FFT)"?

3) How would I represent/draw a the signal at a specific frequency (i.e. 5Khz)? (an online tool would be a great solution.)

a Matlab solution or reference would be great.

Thanks in advance.

[dpb]

Have the Signal Processing Toolbox????