If you are in the region of TSC, you should be okay for it. I spent 5 whole days to prepare 8 recommendation letters and all other paper works. For the 50 pages cover letter, lawyer will take 2-3 hours to cut and paste it. Most of senteces are from your recommendation letters, and other part is previous cases and paragraphs from law clauses.
Only you are famillar with your field. Attorney knows nothing about it. 95% work will be done by you. They only check the format and grammar. Frankly, chinese attorneys' grammar is still engilish-chinese grammar. When my boss read the draft written by me and edited by my lawyer, he laughed and said your lawyer must be an chinese. Anyway, he said he will modify it and let immigation official know he is a local guy.
That is it, try hard,
my friend.