Does saving money on the motherboard matter

If this is your first build, I suggest having a friend who knows more about building computers, to build one for you. One little slip when you place the cpu in the motherboard slot and you can permanently damage the cpu. Same goes for putting thermal grease on the chip, you don't want to put too much on or you could short everything out as you squeeze the heatsink on.

If you don't want to overclock, a Z77 is overkill. The B75 is actually a nice chipset that uses very little power. That matters to some people.
I was pretty impressed with my AsRock Z77 Pro4-M. I've had one of their dual-boards that took both DDR1- and DDR2-RAM and it was a bit mediocre, but this thing is very impressive. Especially since it allows overclocking non-k CPUs. I Think mine allows +5x multiplier.

You have to be pretty ham-fisted to misplace a CPU. They fit exactly one way, like everything that fits into a modern PC. Not like the olden days when people were sticking ISA-cards into RAM-slots.
Very few types of thermal compound are actually conductive. Even the ones with lots of silver rarely are. More likely you put on too much and it results in a couple degrees higher CPU temperature.
Putting a PC together is very easy nowadays. If you respect that you payed a lot of money for these components and treat them that way, you should be fine. Of course asking a friend is a good idea, it might save you a lot of time and it's more fun that way. Though you have to be vary of computer-friends. They're often not as knowledgeable as they seem.

you say overkill, I say well loaded, and Z77 is more than just for clocking

if the price fits why downgrade platforms? who knows what he buys in the future ... and as for power if you check the Z77 I quoted youll find its one of the lowest power Z77s out there, according to these guys who tested 32 ib mobos http://uk.hardware.info/reviews/285...with-ivy-bridge-processors-energy-consumption