3 Heater system questions

[Hair]

1.0 The heater core has one big tube and one small tube sticking out of the firewall to hook to the hoses. Which way does the heater core go in, is the big tube supposed to be on top or bottom? Does it matter?

2.0 Defrost duct hoses: In LMC they have "OE type" hoses for around $30 and then they have hoses for around $15... I guess they're not "OE style". My question is; what is the difference in these ducting hoses? Are the $15 ones better? rubber? don't fit well? come in one piece and I'll have to cut them to length? what is different about them? Why are they $15 cheaper? Anyone know anything about the cheaper ones?

3.0 [B]Heater resistor[B]: What does this thing do? Does it go bad often? How can I tell if it is bad? I cleaned mine up and blew it off and it looks great. I'm putting the heater box back in and was wondering if I should bother with replacing it or not.