Upgrade from7.2.1 to 7.3.3

I have 2 sites to be upgraded from 7.2.1 to 7.3.3 incl set-up of Chat+

The sites are not yet operational but have a certain number of modules attached to.

What would be you price for a secure/smooth upgrade for each of them and how long would it take normally ?

When would you be ready to do it ?

The game would be to upgrade one site then the second one after.

Thanks for your proposals

Jean-Luc