These guides will take you, step by step through the safe removal of what are considered to be the Customer Replaceable Unit (CRU) parts of the various OptiPlex 3080 systems. (CRUs are the parts of the system that should not need an engineer to remove or replace.) The guides will also include pictures to reference what is involved.
If these guides do not cover what you are looking to do, then you will want to reference your System Manual.
If you require further assistance, contact Dell Technical Support