Where would I go to do option 2?
An Apple repair shop
For option 3 are the USB adapters avail at the apple store?
Probably not. The repair shop would be able to help
Would an airport express do the same as option 3?
Not using USB. It would work using an Ethernet cable from the Express to the Mac, but it sounds like you may have a bad Ethernet port on the Mac if Option 1 will not work.
Sounds like the repair shop needs to take a look at the Mac and give you the options.