will you be able to dissemble a unibody designed phone? with the right tools, yes. I used a sturdy thin plastic material similar to a credit card but much thinner to open a sony Z1 and a sony Z Tablet in the past.
I havent seen a phone that requires soldering with battery connection in years, You wont need soldering then. it's likely to have a tiny plug-in-like connector that you can unplug then to replace the battery. Remember to look for the exact battery for the exact model so you wont have issues.