They can be broadly summarized in three steps:
The answer is: "it depends". The complexity of the business, the extent to which the management system has already developed, the amount of time the client is able to devote to the certification project, and many other factors will determine the time taken. After a no-cost, no-obligation visit to your business, I can give a rough estimate based on past experience (which is usually reasonably accurate) but the best estimate will be based on a detailed gap assessment to identify the work that needs to be done.
The answer is: I can usually complete a gap assessment in 0.5 day. Again, this will depend on the complexity of the business and the number of certifications being sought
The answer is: You can, but it is unlikely that it will suit your business. The danger is that the procedures and manuals that you buy will force you do do business in a way that is inefficient or that just doesn't make sense. Another problem with this approach is that because you won't have been involved with developing the system, you won't be familiar with what is in it. That is, what you have said you do may not be what you actually do.
The answer is: There are limits on how fast the process can be done. A certifying organisation will want evidence that a management system has been implemented and is functioning effectively. This can't occur if "the ink is still wet" on your procedures and documents. Six months would be a minimum to achieve certification from scratch.
The answer is: You will need to maintain your management system, by completing internal audits to check the system remains effective, and by reviewing its performance against objectives and targets. I can assist you with this if you wish. Your certifying organisation will visit you annually, or sometimes more often, to check by auditing that the management system is still complying with the standards. Your certificate is usually reissued after three years, depending on the results of these audits.