How to change seed phrase for wallet without transferring coins out of it (gas prohibitive to move them)?

I have a relative who has a wallet that needs to have the seed change. It was exposed. The only reason the coins weren't taken yet is the gas fee will eat up most of the ERC-20 token's value. How could he change the seed to secure the wallet again without having to move the coins off?

bonus question- what is the cheapest bridge out there to move coins from ETH mainnet on metamask to a Level 2 with ultra low fees? Loopring is too much to get a wallet started for him.