Necessary to know C perfectly for uC programming?

Hi guys,
I was wondering if one needs to know almost everything about ANSI-C in 
order to program a microcontroller (consider the fact that I don't want 
to learn Assembler). To explain my point:

I would like to learn C++ because of its OOP. But I also would like to 
get some expierences in programming microcontrollers. From what I have 
seen in uC programming it is (very) important (programming in C) to
- know the bit manipulation for registers
- write and use functions (to make the program clear)
- know about the variables (int, double...)

This is what I used when I programmed a uC a few years ago 
(unfortunately I don't remember much of it so I have to start again 
dealing with that subject).

In my opinion - please correct me if I am wrong - it is not a big part 
to learn.

Okay, to close the circle:
I would like to learn C++ to know it almost by heart and to learn the 
topics mentioned above in order to know how to program a uC.

My question to you is quite easy:
Do you agree with my plan or am I going to do a big mistake with it?

Thank you very much for every answer (and there is no wrong answer; I 
beg your honest opinion about that).

Best regards
al3ko