Nice tut! Pretty much how I do it except I do a few things differently. For one I use the length of 629 for my 14f51 file. Probably doesn't make any difference, but that is what I am used to.
Second thing I do to make the process a tad simpler is instead of making a new file (mission_recomp) I just pack it right back into the original mission_comp file. That way I don't have to re-edit the footer and header. I also have a pre-00'ed out mission_comp (with header and footer in tact, everything else 00) that I pack the 00000002.dat right back into so I don't need to do the extra 00 paste in stuff.
this is what i mean^^^ making it easier for yourself so its faster xD (see post above for 1st part)