Whats the head of the motor for?
 

i have honda civic 2000dx 4dr 1.6 D16Y7 engine non v-tec. im noob as well so i was wondering can i swap this http://boston.craigslist.org/gbs/pts/1026441198.html with mine? would it fit ? and also can i just swap the head from the SI to DX? thanks

you can swap the engine but i believe you need a transmission as well. In response to your second question: no good sir you can not, that is a Dual over head cam(DOHC) head whereas the D16y7 is a SIngle over head cam(SOHC) the block from the y7 is not compatible w/ the head of the B16.

Josh pretty much hit the nail on the head; swapping a b16 into a civic is a simple task. Like he said, you'll need the b16's transmission as well, since the b-series transmissions and d-series transmissions are different.