switching out 60 kWh battery for 85 kWh battery - allowed?

[spaghetti]

pay tax on the difference if you trade it in...

Not in California. Here you pay tax on total selling price irrespective of value of trade-in.

 

[brianman]

pay tax on the difference if you trade it in... prepaid maintenance, who does that when Tesla says no maintenance required??

I did. 4+4 with ranger.