I did NIW by myself, and wrote everything. Petition letter is very important, you definitely need a sample to follow. If you were not a layer, whatever you will miss sth in the letter. Resume also is very important, and in each project you should list you actions or roles in it.
I filed everything in early 2004, and got the card in early 2005. Everything is just easy.
Maybe try get another letter from government department is more helpful.