We just got the vanity and I set it up in about 30 minutes. It took a while to take apart all the small little plastic pieces. I have to say I was not impressed when I saw it in the box- the hair combs & accessories are really cheap- the dryer is ok. What I did not like were all the sharp little pieces left behind on the plastic once u cut it all out. You would have to spend some time filing it all away. Once assembled it is fine, sturdy, but nothing to get too excited about. The mirror came with a big dent from a staple gun or something that left an imprint. The girls play with it so far, but it is not something I would probably buy again.
I gave this to my 5 year old cousin for Christmas and she absolutely adores it. I didn't assemble it so I can't say if it was easy or not but there are several little pieces but it doesn't look any harder then any other kids toy. As for the size, she is of average height for a 5 year old and it fits her perfectly. I was a little worried that it would be too small.