If the chair is wood with just an upholstered seat, it's piece of cake. If the whole chair is upholstered and you have decent sewing skills, you should do fine. Keep the fabric intact (and unstretched) when you take it off so that you can use it as a pattern. You will be able to see which pieces need to be sewn together, and which are stapled on and how it was done. The fabric will need to be evenly stretched from side to side at alternating points to make the fabric lay evenly. I'm sure you can find some videos on youtube. Have fun!