The Nissan Path

I initially put Valvoline DEX/MERC but thinking I screwed up there. If I did a drain, and refill with Valvoline Maxlife DEX/MERC, would that mess things up?

If it wasn't this Valvoline ATF it was likely not the correct one:
https://www.walmart.com/ip/Valvoline-Im ... /267514995

Sorry to be the bearer of bad news.
The regular valvoline is not the right spec... its not like its poison to the tranny like coolant would be, but you should replace it completely.
(have you replaced or bypassed your radiator yet?)

Another proper fluid is https://www.walmart.com/ip/Castrol-Tran ... /176732896

I run the Valvoline MaxLife Multi-Vehicle Automatic Full Synthetic Transmission Fluid in both the transmission and transfer case, no problems with either.