ReadString isn't generic - for strings longer than 0x20 characters it would need to call Dump multiple times and terminate if a block contained a null terminator. This also probably isn't the best way to do string conversion in C# either, but oh well.

Add this to MainWindow:

        public void UpdateItemName(Item item)
        {
            byte[] name = System.Text.Encoding.ASCII.GetBytes(item.Name + "\0");

            uint addr = item.Address + 0x1C;

            for (uint i = 0; i < name.Length; i++)
                tcpGecko.poke08(addr + i, name[i]);
        }

        private string ReadString(uint addr)
        {
            MemoryStream dump = new MemoryStream();
            tcpGecko.Dump(addr, addr + 0x20, dump);
            dump.Position = 0;

            StringBuilder builder = new StringBuilder();

            for(int i = 0; i < dump.Length; i++)
            {
                int data = dump.ReadByte();
                if (data == 0) break;

                builder.Append((char)data);
            }

            return builder.ToString();
        }

Update the initialization of Item in MainWindow::LoadDataAsync to:

                    var item = new Item
                    {
                        Address = end,
                        Page = Convert.ToInt32(page),
                        Unknown = Convert.ToInt32(this.tcpGecko.peek(end + 0x4)),
                        Value = this.tcpGecko.peek(end + 0x8),
                        Equipped = this.tcpGecko.peek(end + 0xC),
                        ModAmount = this.tcpGecko.peek(end + 0x5C),
                        ModType = this.tcpGecko.peek(end + 0x64),
                        Name = ReadString(end + 0x1C),
                        Parent = this,
                    };

Add this to Item:

        private string m_name;
        public string Name
        {
            get { return m_name; }
            set { m_name = value; }
        }

        public string EditableName
        {
            get { return m_name; }
            set
            {
                m_name = value;

                if (Parent != null)
                    Parent.UpdateItemName(this);
            }
        }

        public MainWindow Parent;

Then change one of the column data bindings in the xaml to point to EditableName.