hello, a while ago i also started learning 3d stuff with sketchup, too. its easy to start and checkout if you like 3d modelling, but sooner or later you’ll get problems. i dont know how far, you can create now uv-maps, collision models and lightmaps in sketchup (shadow bugs later). when i was last time in there, it wasnt.
however, if you really interessered in it, get into maya or blender or max. if iam wrong, please correct me. problem ist get into it. thats another thing -.-.
edit:
btw. your modelling looking good. i’ve you’re lucky and going to use blender, max or maya your modells aren’t f***ed up in some kind of way. but its also easy recreating it, if you done it thousand times, with maya, max or blender 
should also say, that my most knowledge with sketchup was with udk 3/ Ro2 SDK. so no warranty about what i said ^^.