sed : help please & thanks :)

I've got this big file and I need to use the sed in one command to do the following ....
1) delete the first 3 lines
2) delete the last line
3) replace nulls or tabs with comma

... is this possible in one command? Thanks

there a lot of books

sed '$d;1,3d;s/[0T]/,/g' input >output

T is litterally a tab char

That didn't do it exactly for me (cygwin in win2k) but:

sed '$d;1,3d;s/[\x00\t]/,/g' input >output

or

sed '$d;1,3d;s/[\x00T]/,/g' input >output

(where T is literally a TAB) does. I assume 0 was meant to be literally a null x'00' but it doesn't actually replace nulls when I try it.