not hard. For me the most difficult part was finding good quality battery cables that were long enough. Most of the pre-made stuff is 4-gauge, pretty wimpy. Get 2 gauge. It seems like you need at least 4 feet, maybe 5 for the starter cable. I ran mine down, under, and in front of the oil pan, just below the block, and got some clips to hold it tight. This is important, you don't want that sucker hanging loose!

The negative is easier, it can go to the engine block on the exhaust side, it's a shorter run. I think i connected mine at the motor mount? just stay clear of the header/manifold! Also you'll have a ground going to the body, that one is like 12".
You'll have to fab up a tray of some kind too, I got a $5 AZ cheapie, and ran a strap through/over it to hold the battery to it.
Only downside to how I have it is (battery) kinda leans up against the coolant resovoir. It's prob okay like this, just bugs me.