Wiggle the PSU connectors back and forth until they loosen up and twist heatsinks back and forth until the cemented thermal paste breaks loose. Good cable management inside your case can make *** easier too. Sure, it takes like 5 god damn hours to get it all right, but it's worth in the long run over the years.
This is good darn advice, shouldnt take 5 hours though
I cant remember how long i've been taking apart and building pc's but as long as you do you prep work it should be all ok.
Also nothing should creak or crack, do it all gently and you will be fine!