You can get some guide books out of the library.
I don't know hwo small your budget is, but I am amazed as to how much people spend to go somewhere, then do not buy the $50-100 of necessary guidebooks and maps that really help plan the trip.
My preferred guide books for Paris are:
Access guide to Paris
Zagat Paris
Michelin paris red book
Guide to small museums of paris.
Any old Fodors Paris for the top tourist spots.