74 Duster Heater core swap tips

Hey guys, My windows keep fogging up on me when I use the heater in my duster, so I feel down around the heater box and sure enough its leaking. I've watched some youtube videos and did a little bit of research online to find a good tutorial on my car. The process seems pretty straight forward, but this is another one of those tasks that I've never attempted before. I'll be sure to buy a service manual so I won't bother you folks as much in the future.

Any advice on putting the new one in? Thanks for the help, Everyone have a safe weekend!!
Author: scott2683