I agree with the above posters. I think you'll do just fine. My company had a temp fill in for me while I was on vacation a couple weeks ago, and she was so smart (she has a Master's Degree, yikes!) and professional-looking that I felt a little overshadowed.  But I was happier to have someone who caught on quickly and did the job well than someone who would have left a mess.  They still missed me while I was gone--because I tell you what, no matter how good the temp may be, there is still only one YOU!