hex replace in autoit

Hi everyone

I have 2 basic question about hex editing

- I have several texts with a common problem, in stead of having CRLF (carriage return+line feed) only had 0x0A (LF), how do I add 0D behind every 0x0A?
- Its possible to edit only the beginning of a file (speaking in large files that should't be loaded in memory) and save the changes?