Don't trust me. In fact - don't trust anyone, ever. Scan the USB with your favourite anti-virus software. Do any other tests to make sure you're 100% safe.
Maybe you could checksum every file on the memory stick and then sign that with a PGP key so that people know that nothing has been tampered with?
You definitely sound like you know a lot more about what you're talking about than I do. I don't have a PGP key per se but I have old bitcoin addresses that I've staked here on bitcointalk.
Any suggestions for how I could checksum every file? I've never done it before.
Yeah there's nothing stopping you signing it with a Bitcoin address instead of a PGP key.
Not sure what the best way to checksum every file on the disk would be, possibly something like
find / -type f -print0 ! -name "sums.txt" | xargs -0 sha1sum > sums.txt
After that, people can verify everything with
sha1sum -c /path/to/sums.txt
You will also need to sign sums.txt with your Bitcoin address otherwise it would be a bit worthless. Good luck