one of my projects involve a flythrough in a photovoltaic farm which consists of thousands of panels all the same shape and size and orientation.
the best way would be to use the link command and then array the objects? (Ctrl Alt O)
i already have the model in sketchup but to get a clean model i guess its best to redraw everything… 
yes you should add one array modifier for vertical and one for horizontal assuming you want a grid. as far as remodelling it, it depends. if it’s simple enough, sketchup probably does an ok job. the main thing is how well it renders.
Depends on what you need it for. E.g. if you only need it to render that flythrough of yours, maybe you don’t need to trouble yourself remodeling. On the other hand, if your model is messy and has lots of polygons, your performance will suffer when you array it. But even then you don’t need to remodel completely from scratch. You can use Blender’s retopology tools to (relatively quickly) build a new model. Namely surface snapping and BSurfaces.