Convert c code into Cuda

I am a new cuda programmer. I want to convert a project written in c-language into cuda. the c project is implementing the parallel heap (with mollions of items). it contains some linked files. the basic construction of the project based on pthread.

my primary concern is not to start coding and spend long time trial and error but discover latly it is not doable!
the other issue i am thinking of is due to due dates I am restricted with, I dont want to do the whole task at once. but rather I may convert main.c into and keep other source in .c format adn link them with .cu code . is that possible?
the last think to plan for is the memory! which memory I have to work with to be sufficient for such problem?

I attached some files for rference.
Thak you
parheap.h (3.04 KB)