[CentOS] Vim scripting - cursor motion

I am working on my first vim script. The script is supposed to do some find/replace on a file, then save the file with a new name and quit vim.

I will save the script in a file and then call it from a bash script like this:

vim path-to-the-file -s path-to-my-script

Maybe I have not found the right resources. I can find/replace with expressions that are similar to those I use manually, for example:

:% s/\t/","/g

Then I should add something to the beginning of file (line 1, char 1). And append something to the end of the file (last line, last char). But I cannot find a way to do this. Should I move the cursor (and how?), or what?

- Jussi