RE: HL IR system
That kit is for converting older tanks to IR (meaning those with RX13- and RX14 boards inside).
Best way for a plug-and play conversion is trying to find a complete IR turret. That would be an almost plug and play conversion.
Otherwise you won't be able to convert completely your tank to a standard Heng long IR out-of-the-box version, unless you also buy a recoil unit.
But if you already have an RX18 inside your tank you don't need many items from that kit.
A: 1 x RX-18 Multifunction Board. < NO NEED
B: 1 x IR Sensor Tower Mount ***NEW ITEM***
C: 1 x 3pin - 3pin cables.
D: 1 x 8pin Connector Harness.
E: 1 x High Voltage Flash Unit. < NO NEED
F: 1 x IR Sensor Tower.
G: 3 x 2pin Red/Black cables. < NO NEED
H: 1 x 8pin - 5pin cable.
I: 1 x 8pin - 8pin cable. < NO NEED
J: 1 x Standard L.E.D w/wire.
K: 1 x TK-YL101-1 Receiver Board with 3pin-3pin < NO NEED
Other items are not a plug and play system, since you have to put the IR led somewhere and so on. And you will still retain the BB shooter.
As I said, easiest way is buying a complete IR turret.