There is more than just the conversion and soft-proofing. You need to know and deal with, among other stuff, screen frequency (and sharpening for that), the paper - coated, uncoated, etc. - that will be used, whether or not there will be a varnish applied.
You can prepare you files as best as you can, then get the printing house to send you a proof from their system, it is usually considered that such a proof is at least 90% accurate and is fine for printing “pleasing colour”. For accurate colour, you will need press proofs, and maybe be at the printing house to check and approve the actual press run. Not a cheap process!
Your best friends in this case are the pre-press people at the printing house. They are the best people to guide you in this process.