With reason. That glue is a nightmare to deal with. I would not advise anyone start with iPhone repair.

I damaged my first iPhone repair even after multiple years of active hardware modification on other consumer devices. The older models really only go smooth if you have the Apple tools. A nice $149 of tool rental to swap the $50 part at home, rather than paying the $199 to get Apple to swap it for you. Odd how that math works out.