One piece at a time is the right way. You would be surprised how many people want to jump right into the deep end where the rocks are.
Combining sketches is not a big problem. I strongly recommend that you put as much as you can into discrete functions no matter how trivial they are. It will make combining the sketches much easier later.
30 years? You're a youngster. I cut my programming teeth on Fortran 2. BASIC had just been invented. I started my programming career using HPL.