Joshua, yes indeed there's a pre-made cable but if you're comfortable splicing and soldering yourself (like me) it's really not hard.
If you have any questions about the wiring just hit us up here but it's pretty basic... video+gnd comes off the Phantom mainboard (the colored cable that originally came taped to the bottom) and goes IN to the iOSD, then there's a video OUT (+gnd) that goes to the vTx. and separate from that of course you're got power+gnd out from the Phantom mainboard (same cable as video) which goes directly into power+gnd on the video Tx.
There will be a few extra wires on the cable that comes with the TS352 that you can just cut off, like audio in (green+white) and VCC+ out.
The Boscam indeed theoretically puts out more power but it also eats more power, most folks around here say we're talking about a dozen or 2 seconds of flight time... not a huge deal. I'm perfectly happy with my TS352 and yep it's cheaper. Use channel 1 you will have to flip all 4 dip siwtches. by default they all come off and channel 1 is all on.
Then on the RX-LCD5802 it's channel C-1.