Mostly yes. That's if you look at something like 'MAKE OBJECT SPHERE ObjID, SIZE', in GDK you would just simply convert it to 'dbMakeObjectSphere(ObjID,Size);'.
Functions are only slightly different too in GDK, but when you get the hang of the change between Basic and C++ you pick it up easily enough.
There are a lot of plugins available for DBPro that you would have to do yourself in GDK but C++ has all you need for that anyway.
EDIT: Only when it comes to splitting up your source files it can at first become confusing but the general C++ tutorials will more than suffice to help you understand that part.
Warning! May contain Nuts!