adjusting the notes of a song

[Tony Costine <acostine@xxxxxxxxxxx>]

Hi, new to the group (hi group!). Was playing along with some of the tab on
Harmonicacountry.com and found myself being bothered by the high notes used.
Read where you can convert straight harp to cross harp tunes by subbing
notes.
Tried to create a version of Danny Boy (that well known blues classic!) in
cross--a version I could play that didn't use the 7 8 and 9 hole...but am
having no luck. 
Is trying to convert songs like this a fools errand, or is it possible and I
just don't know enough yet to do it (certainly probable!)?
Any help would be great,
TIA,
- --Tony

Also, any other sources of tab on the internet I haven't found yet? I think
that it's helping educate my ear.