Not that I have removed a loom fully but it would just be a case I guess of removing the lower dash to aid in finding the grommet in the bulkhead and feed to old one through after of course removing the ecu out of the holder and the one I think above it and its cradle which if I remember rightly is held on by a couple of bolts???

And with the new loom labelled up it'll be well easy.

Hope this has been some help