Ask 美國老土 and everybody: about contract job agreement and referen

I couldn\'t open the 101 in your blog. So ask you the following questions here.
----An agent would let me to try a contract job (about 6 month). But I have to sign on the agreement first . Is it OK?
---- about the reference, since I have a long period of gap, can I just give an old coworker\'s (not supervisor) email?.
----And my last job has little to do with the one I applying now, Is it useful to provide it for the reference?
------ Can you give me a sample of reference letter?