Cathedral - Is the market replenished by the player or by the bank?
The Struggle for Catan
The market is always replenished by the bank.
Note: The Cathedral isn't part of the regular card pool.
Merchant Guild - In which phase may I use the Merchant Guild?
The Struggle for Catan
The use of the Merchant Guild is not confined to a particular phase. Therefore, you may use the Merchant Guild at any time during your turn, even immediately after you have built it.