Hello,
there is not so much work, I would like to do it for you in some hours.
About the downtime: this is mostly a question about the setup of your current VPS provider. In normal case there will be no downtime at all (or maximal few seconds for a switching), because we could organise both servers to work a while in parallel, both using the database from the new server, previously migrated there. But unfortunately, some providers block external connections for customers mysql services, may be on some internal technical requirements or on some ideas about safety. If it is so, you will need a quite longer downtime, in about a hour or so, depending on your data volume and other circumstances. Also, to tell you exactly, I will need to look in the current system. But, I think, one hour downtime will be the worstcase.
Please contact me if you are interested.
Best regards,
Viktor Gotwig,
Cologne, Germany.