Re: what happpen if you replace an animal cell nucleus with a human nucleus ?

Although some element are highly conserved in all animals, (DNA 
polymerase, for example) the overall genetic similarity between a human 
and another animal (except primmates) is low.  As we go further out on 
the branches of the evolutionary tree, there are fewer conserved 
sequences.  Even though the nucleus controls the cell and codes for it's 
proteins, it relies on proteins for control and replication. 
So to answer your question: It depends on which animal you want to put 
the human nucleus into, but most likely the cell will not be viable 
because the nucleus could not communicate with the existing proteins of 
the host cell.  If, however, the host is similar enough to the human to 
communicate (and induce cell division) the cell would produce it's own 
proteins and after several replications would very much resemble a human 
cell in both make-up and behavior.
As a side note; I'm not sure (since you chose a skin cell) if you were 
interested in human cloning.  The idea is the same, except the nucleus is 
put into a de-nucleated unfertilized egg of a human.
I hope this answers your question, but if not please feel free to 
elaborate or ask another question.
The following link describes evolutionarily conserved elements in 
vertebrate, insect, worm, and yeast genomes. you can review the 
highlights (after the abstract.  http://www.genome.
org/cgi/content/full/15/8/1034