TBLexus01

I have a 2001 Lexus GS300 that I purchased 3 years ago. Since then have replaced the battery twice due to complete drainage issues. Now the positive terminal keeps coming off and once I reattach or punch it back down the car will start but engine pops. The last time I reconnected the terminal all of the lights and display for my radio went out.
My positive terminal is corroded and the clamps and screws are stripped!! I want to replace this myself but it looks so complicated. Plus I have been told my ECU fuse needs replaced. What is that???

Can anyone please help me with part number or picture of correct Positive terminal replacement part and what fuses I need for the radio display and reader. Also what and where is the fuse box located with the ECU fuse and Ignition Fuse and what those are?

Thank you.