Hi Wilclean,
Have to agree with Andy on this one im afraid, restaurant carpets can be problematic, especially for those who have no experience, there is too much of "im a cleaner, i clean everthing, dont need experience or training" in the industry as it is, if c/c is something you want to get into, fair enough, get yourself trained and properly insured, in this instance, you have a regular contract with windows and the cleaning maybe, be foolish to take the risk in my opinion of doing the job, and leave your new client witha poor perception of your work.
If you pick your contractor carefully, he may even let you help on the job, and begin by showing you the ropes as it were, then when it comes to the training, you will have a head start so to speak.
The reality is though, as Martin stated, is that most people, just go ahead and do the job anyway, no training, no experience etc, at the end of the day, this is one of the reasons why a lot of clients have a hard time picking good contractors, they believe that all cleaning co's are the same, the only difference, being price.
Whatever you decide good luck, regards,
Rob