Your camera will not delete or overwrite recorded footage unless told to do so. Reading your product's manual will likely help answer your question. Page 32.
Thanks for the reply.
You won't be able to erase a Mini DV tape in the way that you can erase or format a memory card, but you can record over the prior footage. Simply rewind the tape to the area where you want to start recording, switch back to the camera mode, and press record.
Hope that helps.