The simplest form of Windows programming will be C. You should then learn C first. But if you really know C++ already, you should know C or be very close. Maybe brush up a little on arrays and memory management? In general it shouldn't be too hard. Just remember a few tricks: STL's std::string.c_str() returns a C-string, equivalent to LPCSTR, std::wstring.c_str() does the same but in Unicode (LPCWSTR), and most implementations of the STL allow you to get a C-array from a std::vector<> by means of &vectorVariable.
Do yourself a favor, take those suggestions from webJose write them down on a sticky note and super glue it to your monitor. They will save you SO MUCH heart ache when you're working with Windows and since the strings class is C++, you'll never see those suggestions on MSDN.
There is really no reason you can't make your own classes for Win32 "objects". In fact I highley suggest doing this since nearly every struct has a related HANDLE\HINSTANCE etc. (that isn't part of the struct itself but is probably required for what you are trying to do) and calling CloseHandle() is a necessity for each instance of these HANDLE objects. This can easily be put into a destructor and I feel like doing so will teach you more about the API, and help keep everything neat and clean.
EDIT: Also remember that a HANDLE is a void pointer so don't try to copy it into your object otherwise closing it won't do any good.