Note: Not an expert, but I have installed both kinds of these.
OK a few things, the one you listed is a bypass humidifier - basically you hook it up and you do a small hvac run so air passes through the wet sponge of the humidifier. Its a more passive system.
I have this on my house: Honeywell HE360A Whole House Powered Humidifier. This one has a powered fan that blows the wet air into your system. IMO it is a better and easier to install product. You do have to cut a hole in your furnace plenum, which requires drill bits and tin snips (WEAR GLOVES!) Its tricky but not hard. Also be super careful with your drill, if you drilled into your AC coils you would have to replace them which would be terrible! It might be better if you could pull off the panel to your plenum to see exactly what is behind there before you start to drill and cut.
After cutting the whole follow the instruction, its not too terrible. This unit does need a plug nearby, so that is something to remember. You also have to tap into your water line with a saddle valve (you probably already have one for your icemaker) There is a little wiring that has to be done but its low voltage and you will just leave it unplugged until you are all wired up. You also have a few pressure switches and the humidistat to install, but again just follow directions it is not terribly hard.
A complete noob could probably accomplish this in 4 hours. I would recommend having a friend help you out, not because you need their labor, but it helps to have 2 brains working when your new to something like this! Watch a few videos and you will be fine.
On the warranty, I am not sure the manufacturer is going to care how it was installed. I highly doubt that they would 'check your work' so to say. There are very few moving parts, and a failure of the product probably just means that something got clogged and needs to be cleaned out.
Good luck!