Hmmmm....well, when we play Orochimaru Vs Minato, we have to realize that its Orochimaru(the cocky dude who let's his enemies get him just so he can screw with them when he doesn't die) Vs Minato(dude who doesn't everything in his power to end fights as quickly as possible) so chances are Orochimaru would be as careless as usual.
Now onto abilities-
Orochimaru shooting snakes out of his hands is countered by Minato's immense speed(I mean even Yamato could dodge those and marking one of the snakes will allow Minato get the drop on Orochimaru since the snakes usually retreat back into Orochimaru's sleeve when they miss.
Orochimaru's Wind Release: Great Breakthrough will be countered by Minato blitzing him to prevent him from getting the chance to do it. I'm not saying Minato is like Mifune(who specially trained to take advantage when an opponent is forming seals) or anything but he did however move fast enough to save Naruto from a point blank kunai attack from Obito and he also carried Kushina away from a point blank claw attack from Kurama when the fox was under Obito's control so its very likely he can close the distance between Orochimaru and himself before the Sanin gets the chance to do much in the way of forming seals for his jutsu. (Even Sai could blitz Sasori AND Deidara before they could do much and I don't he's faster than Minato.)
And even if he does perform this tech, Minato can evade(even kid Sasuke could)
As for Edo Tensei...well, Hashirama and Tobirama are no joke however...they are very absent minded as the Third could tag them with explosives and they didn't even notice. Also, there's the opening of when they're standing still like statues while Orochimaru places tags in their heads. Minato could blitz mark them, or just seal them with the Eight Trigrams Seal he used on the Nine Tails(yes, it can work on people too and it has a good range since Minato intended to seal Kurama from a distance so great that the fox had to stretch the full length of its arm to reach baby Naruto(and we all know Kurama's got a pretty long arm) so Minato could stand a good distance away and seal them, heck even seal Oro along with them. There might be doubt whether the seal will actually work...why wouldn't it? Why would something capable of sealing half of Kurama and what was left of Minato and Kushina's chakra into a baby not be able to seal three humans(two Edos and Orochimaru)? I bolded it cuz I go into a bit of detail about the Eight Trigrams Seal.
Now if their powers are unleashed, that'd be really bad but at some point, taijutsu will ensue. After all, Sandaime sliced up the Mokuton and apporached the two Kage at which point he marked them with explosives to make them explode, Minato can evade the branches with FTG then mark them with FTG instead of explosives. They won't know better since they're mindless and Orochimaru won't care since he even let Sasuke roast him with a Katon jutsu and let Sandaime live long enough to prep the Dead Demon Consuming Seal and didn't use Kusanagi against Naruto when the jinchuuriki was in one, two and three tails.
Also, counting these Edos as part of his strength is...iffy.
Orochimaru's other abilities? Well, Formation of ten thousand snakes is basically ten thousand snakes slithering towards you. Minato can have Bunta oil them all to prevent them from moving then jump over them and get to Orochimaru.
Manda, huh? Bunta's proven more or less a match and then there's Minato who can support by using Space time barrier to help the giant toad. Now imagine if Minato lets Manda swallow him then summons Bunta in Manda's belly to tear the snake apart from the inside? Easy victory and Manda is Orochimaru's strongest snake.
Kusanagi, just dodge it and mark it. When he eventually swallows it, teleport to him and tear him apart then seal him before he regenerates.
Orochimaru's Eight Headed Snake Technique. Well, its slow since it was moving in pace with a battered and sick Itachi who's chakra was nearly depleted and was at death's door. The heads were torn apart by Susanoo so Bunta can do the same and Minato can just seal it.
Hmmmm.....not saying it'll be easy as Orochimaru is quite the tenacious fighter and possesses a plethora of ninjutsu at his disposal however, the Fourth's speed and powerful sealing technique(the Eight Trigrams Seal) will work inevitably work in his favor and I believe will lead to his victory.
This is all just my opinion(based on fact ^_^)