how do i get the coolant level sensior out of the bottle?

With coolant resevior still in car.Use a pair of long nose pliers put the ends of the pliers into the side of the overflow bottle you will see 2 holes opposite of each other,spread the pliers and insert into each hole and undo with the pliers.Becareful not too slip,may injure yourself.And remove the float level and nut.Make sure before you install the new one to fit the new "O" ring and nut before you fit the sensor,fit the nut over the sensor before refitting. and just nip up with the pliers same way that you removed it.Hope that helps.

or use a 4" angle grinder wheel tool
fits perfectly into the 2 holes