Don't stress much! If you look at the Blichman sparge arm, it just is a tube that floats on top and gets the sparge water flowing across, rather than down. I used that method for 10+ batches and it worked really well.
Now I have a new rig and am just using a copper pipe with holes drilled on it and the end is crimped and soldered - water flows in and dribbles out so it just sits on top. Works great, is extremely simple - worked for 5 batches so far.
Yours looks nice! I take it that it will go through a hole on top of your mash cooler?