I was in the same position with my product and didn`t want to spend money on something that may have been only worth somethong to me. I wanted to do it all myself either because I didn`t know better or thought it would be a breeze. I purchased a book called Patent It Yourself by the NOLO company, can`t remember how much it cost (2004). It was very thorough and if you have the patience, time and able to afford attention to detail it can be done.
The whole process took me approx 6 months. The two main points that I can stress and that would have saved me time is you will have to spend money on professional patent drawings and you must be willing to deal with the Patent Office. There is red tape you`ll have to deal with and you will get rejected by the office until corrections are made or more detail is needed, improper wording correctied (claims), and various other info corrections the examiner may not like are corrected, you`ll want to give up but the book covers everything from evaluating your idea, dealing with Patent Office rejections to final patent submission and acceptance and then what to do with your patented product. I don`t work for the company or sell their products, all I know is the book helped me get a design patent with minimal amount of money spent.