A level editor is a good start, and some test level pieces. The collision detection can be tricky when dealing with weirdly shaped pieces, but a simple ground height arrays tends to work and is real fast. It's sorta like pixel perfect collision but more stable and faster. You'd have a row of heights for each piece of level, then you simply check these heights with the player.
Could you post some screenies of your sprite work, if you have any sprites you have drawn yourself that would suit a Zelda style 2D RPG, then I could really use them. Working on a Pokemon rip off RPG with my son and little brother, I'm sure you can imagine what crazy ideas an 8 and 10 year old will have

. I'm thinking one or two enemy sprites if you have them.
Van-B

It's c**p being the only coder in the village.