Best route is to take out money from ATM or exchange at a money exchange. Avoid exchanging money at the airport. Most restaurants and cafes accept credit cards. Try using a credit card with no exchange rate.

There are multiple buses from Skopje to Ohrid every day. See schedule here: https://getbybus.com/en-us/skopje-ohrid. It costs roughly $25-$30 for a round trip. If you gather a total of 3-4 people, you can take a taxi to Ohrid.

No, you'll have to catch a cab on the street or call one from a local number. Skopje: https://zk.mk/taksi-kompanii/skopje Ohrid: https://zk.mk/taxi/ohrid?lang=en Area code is +389-2 for Skopje, +389-46 for Ohrid.