Spoiler Help??

I know this should be simple but I want to go by and check and make sure of what to do. I want ot replace my stock spoiler with another fibderglass like a Battle of a Combat type... when I take off my stock spoiler will there not be holes left and displayed when the other one is put one?? where should I take my spoiler to get it mounted and the wholes fixed?? I plan on painting the car anway so does it needed to be welded back in how much is all this gonna run me for the installation and welding?? thanks