I understand that the underlying consensus model changes from PoW to PoS. However, will it also result in changes to how wallets interact with the network? Will transaction fees still have to be paid to get a transaction processed?
The economic mechanism for how transaction network inclusion works will not change.
The difference lies in how the network confirms the transactions and arrange blocks and that is a responsibility beared by special nodes.
Right now --> this responsibility is placed on 'miners' who arrange and confirms blocks through mining.
In Serenity --> This responsibility will be placed on 'stakers' who will stake a minimum of 32 ETH (according to latest details) and they will earn “interest” and fees from forging valid blocks (randomly in proportion to the ETH staked).