Beam profile may suffer, owing to the LED placement (not mounted on the middle of the heatsink, rather on the side).
However, I'd not mind, I may do that on my Brinkmann Q-Beam pistol lantern (I tried to fit the HID kit in it, turned out to be an awkward placement as the igniter tend to be large and the ballast option is the aforementioned software-defined slim AC ballast - the HID kit went into Thor Colossus spotlight instead, probably the same host you're using).
Wiring is quite simple, however, similar to Halogen bulb you're ditching. The owner's manual would point out the wiring if it's a dual-beam option.
As for the battery, if you want longer runtime, ditch the Lead-Acid battery and get a protected Lithium-ion battery pack and the appropriate charger for it (I'd recommend to fuse it with around 8 - 15 Amps fuse, depending on LED driver current consumption, as Lithium-ion bstteries are actually much more powerful than Lead-acid battery owing to higher peak current which can cause damage if you make a wiring mistake).