I’ve modeled a decent wreath, but I want to import into a scene which already has a lot of objects, textures, etc. And the wreath has a lot of vertices, because I created it with a particle system and then converted it to a mesh. Is there a way to reduce the number of vertices, but still keep the integrity of all the little needles, etc.? The other scene is already bogging down Blender performance, and the wreath file even by itself is slowing down Blender a lot, so if I combine (append) the wreath, I would be almost certainly too much for Blender to handle.
You can try the decimate modifier, lower the percentage to find a balance between quality and vert count. Then apply it. Sometimes on jagged objects like wreathes it actually looks better decimated.
Also use “Remove Doubles” from your tool box. May need to increase the distance just a little bit.