First of all, it will be easy, because you have somehow worked in the field of electronics.You need to get yourself a good reference book to study from.You have got a host of books which gives you information on programming the 8051/52 in assembly,C language or both.If I were you, I would opt for Mazidi & Mazidi.Once you are thorough with the basic operation,hardware design and programming, try them out on a breadboard.You can even get yourself a trainer kit to understand how different interfacing works for 8051.As you get more proficient in the design and programming of the 8051,start designing your own systems.

Its a long way up,but i guess very fruitful and interesting at the same time...ALL THE BEST