I have many small planes, which I want to merge into one smooth surface. I did some search and found "dissolve" is probably the way to go? Here is my simple .blend file.
Use the Join tool.
Object mode , select All.
Ctrl + J to join all the parts.
Edit mode, with all selected. open Tools panel.
Tools tab > Remove > Remove Doubles.
Shading tab > Normals > Recalculate Normals.