04 Nissan XTerra wiring

I am in need of a bit of help and you'll have to forgive me if I am fumbling through this. The answer is probably easy.

I got a new 350 Watt Power inverter. It gives me two options. Either hardwired to the battery or to plug into my ciggarette lighter. However, everytime I plug into the ciggarette lighter, it blows my fuse. I tried putting a heavier fuse into it but it blew that one too so I thought I would try hardwiring. The problem is...I can't figure out where to get my wires through the firewall so that I can connect it to battery. I'm a bit scared to remove the dashboard but I can't seem to find another way through. Am I missing something? I've done numerous searches on the internet for a diagram and almost said screw it and got out my drill...but I'm a bit nervous about drilling a hole in the firewall without knowing what's on the other side.

Can someone help me fumble through this? This can't be this hard....is it?

P.S. That's what I get for watching all of these American Hot Rod shows and thinking I might be able to do something like that....

If your drilling, have a buddy tap really hard on a free spot you have on the inside on the engine bay, and you match that spot up on the inside....like Flakman said, look for things that you recognize on both sides.....drill a small guide hole....and have your buddy said (or double check yourself for clearance, and free from heated objects and obstructions)), THEN you can drill your hole to size and put a grommet and some sealant if you want to, good luck

Sometimes I use a center punch to mark where I want to drill.  Once you're sure you're clear of obstructions, drill a pilot hole with a 1/8" or so drill bit, and enlarge it with a Uni-bit.  If you know you can drill through the other side, but don't want the drill bit to go too far, you can put a bunch of tape around it so it'll stop when you reach that depth.