C++ is very little different, and is basically a superset of C, so if you're fairly familiar with C, then C++ is easy to move to. If you're spending 12 hours a day learning it, then it shouldn't take more than a day (if that).
Perhaps get an Arduino/, and have a play with that - as it uses C++.
However, if you're moving from normal Hitachi type LCD text modules the change to graphics modules is considerable, but nothing to do with C to C++ - bear in mind you can just write in C under C++.