Craig
This job is no different than the first job you quoted for, yes it is bigger and hopefully it will lead to other bigger jobs in the near future.
But I am afraid that you need to get burnt at times in this game, we all learn from this site and others, on cleaning equipment, jobs and pricing but at times the best information we learn is from doing the job.
When I first started, I looked at the big jobs and went with my gut feeling, if I thought it would take 3 days, then I would quote for 2 days work, because I know that in the future I will get faster and thereby my pricing should reflect this.
If I lost the quote I always ask for feedback from the companies concerned including the final price they went with, this is a good to fine tune your quoting abilitys, also if I got the job, I can still learn if my prices are too low or right for the work involved.