Modeling gears in Sketchup is really just combining some very fundamental modeling tools and operations. Radial Array is probably the trickiest thing if there’s anything tricky about modeling them. Working with the gear centered on the origin is a good idea and it looks like you did that.
Whenever I’ve wanted to draw gears and such I’ve just done a search for ‘gear dimensions’. You’ll find various sites that give specs regarding tooth shape based on the class of gear. Generally for small gears, especially for 3D printing, I will work at a larger size. If in metric, I’ll use meters instead of millimeters. If inches, I’ll either use decimal units and move mental move the decimal or work in meters as if they are inches. For 3D printing you’ll export an STL file which is unitless and you just need to import it into the slicer with the right units. You can model in meters but import into the slicer in inches if you want.