Make 2003 Suburban tow better?

[jesdude7789]

What would you guys do first to make an 03 suburban tow better and feel more sure footed on the highway when towing anywhere from 2000-8000 pounds?

I'm thinking I need to replace the rear shocks but I also feel like the stock rear springs are just too damn bouncy. The 10'x5' trailer I use right now isn't the best condition and acts a little squirrely if it isn't loaded just right so i'm looking at getting a light duty tandem trailer to help improve the highway ride as well. I would love to have a 2011 and up F-250 but it just isn't in the budget right now. I want to install a trailer brake controller in case I am using my father's heavy duty 18' trailer that weighs 3000 pounds just by itself. Are those just plug and play on this year suburban or does it require splicing wires?