The fact that you never run out of lights over a weekend doesn't tell much. When the battery voltage drops to the level when it can't support the lights anymore - it will be too low by then, nobody treats his battery like that.
45W is almost nothing. The amount of energy that it will collect on a sunny day, will all go to feed 12V circuit of propane fridge. Or - a small TV set. But not both. So if he wants a TV every day, the battery will still lose the charge slowly. But, if the goal is to stay generator-free for a weekend, by all means, get that 45W. Or, better yet, buy another battery, it will hold more charge that 45W panel will collect in 3 days.
Yes, 45W charger from HF is complete, since is not meant for roof installation. You point it to the South and clamp to the battery. I think they even included the cable with crocodile clamps - it's cheap in auto parts stores. Then you come back to find that it "grew legs" :)...