If you just bought it my personal rule of thumb is-never repot for a full year. Laverne plants them slightly overpotted..fine for a greenhouse,but outdoors the slower pace means the root system takes an additional year to knit the soil together.
Chances are if you knock it out of it's pot right now-even to just put in a nicer same sized pot,the rootball will fall apart killing the tree.
If you hate the look of the nursery pot..just put it in the cover pot of your choice.
As far as next year's planting out-wait until its gone through 2-3 flushes before planting in ground. You really want a solid root system.

Thanks! I dont mind the black pot at all. I have seen pictures on this forum of fruit trees still in pots but I wasn't sure what size or for how long they should be there. I will keep it in the pot it came in for the next year and go from there. How long before I get to enjoy some home Mangoes?

A Laverne Manila can flower in less than two years. In early spring to May to flower,a few nice fruit off a young tree by the middle of June and a smattering all the way to September or beyond. By cool weather the left overs can be used for dishes that use green or sour Mangoes.