It's not an easy task but you're already demonstrating the mindset required to be successful at it. The key is to be a leader and not a manager - use your rank for their good and they will support you (for the most part, there's always a shithead or two who likes to learn by the stick instead of the carrot).
I took command of a unit that I had been a Captain in a non-command position in for three years; I feel your pain on this one. Be prepared that even if you are 100% fair and equitable across the board, your poor performers are still likely to point the favoritism finger. Don't get disheartened, the good ones will see the good that you are doing and you need to come in everyday energized to do good for them.
90% of the issues can be eliminated through communication, you just have to get through the awkward phase of directly communicating standards, expectations, and boundaries. This can be especially awkward if clear/direct communication to subordinates is not a part of your department's culture. Something to the effect of "Hey guys/gals, I'm still the same me I've always been, I just have some new responsibilities now. I want to be the best Sergeant that I can be for you guys. This is going to be a transition for me, please be patient with me and I promise I will treat you all like the professionals that you are. I look forward to sitting down with each of you individually to talk about how we can best work for each other and make improvements around here". At those individual talks, you can break out the "hey, I know we've butted heads in the past but I want you to know that I don't hold any grudges, I ask that you do the same" or the "Hey dude, I know we are best friends and you've known my kids since they were in diapers, I need you to know that I am going to be completely equitable across the board."