I was asked to make a half sheet cake and a smash cake for a birthday party. I am use to large round cake orders but not sheet cakes so i have a few more concerns.

My first question is, would it be better for me to go out and buy a half sheet cake pan and heating core rings or just use 13x9 and double up?

My second question is do you guys normally make sheet cakes one layer or two? (She is needing to fed about 40 to 50 people)

My third question/concern is I am going to be working a lot the week the cake is need on. I was hoping I could make the cake the weekend before and ice it probably Thursday and give it to her on Friday (party on Saturday). Would this even work? I don't want the cakes to get dried out. I normally bake wednesday and wrap them well and refrigerate over night and decorate Thursday night.

Thanks for all the help!

Why don't you bake it and freeze it? Would rather do that than leaving it out for a week. My guess is it'll be very dry otherwise. 

I've never froze cake before, would I just wrap it in more layers of plastic wrap to protect it? Take it out that morning for it to thaw?

Julia1812 is right, freeze it.  First you would want to bush it in simple syrup, then wrap it well in the plastic.  I also finish the entire thing with tin foil. Better to over wrap than have your cake ruined by drying out. If you haven't made simple syrup, it is 1 cup water and  1 cup sugar.  In a medium saucepan combine sugar and water. Bring to a boil, stirring, until sugar has dissolved. Allow to cool.

Yes^^^

Never used simple syrup before though. I wrap my cakes 5-10 mins after they come out of the oven in cling film to prevent the moisture  (=steam) to escape.  Then I cool it down and freeze it once cold. 

Also am rather using more wrap than necessary just to be on the safe side.  You can even freeze (crumb) frosted and fully decorated cakes. Place them in a box and then wrap the box in many layers of cling film. Just to be sure to get rid of all the condensation while thawing BEFORE you take it out of the box.