Advice regarding import of old (but current)data to new system

Looking for advice as to best practice, or pitfalls to avoid.

We have a relatively complex solution in 2.1.3 which is our production site. As such it is being updated (content) daily..

We have upgraded the site in development (in order to meet the local disabilities act) which has resulted in new fields in some tables, upgrades to plugins and extensions etc.. We have also moved to 2.10 in order to make use of the newer plugin versions.

So we now need to bring in the current data from our old system before we can make the new one production state…

Are there tools which make this easier, or which at least enable one to analyse table structure and field counts in order to facilitate such a move?

I assume the best option would be to first replicate my productions server and bring it up to 2.10.

I will then need to do individual table imports, otherwise I risk overwriting the template changes made in development.

Any advice appreciated! Thanks in advance..