It depends on how much time you have and whether your design is detailed or more simple. Its not too hard to make your own but maybe it would be easier to find someone who makes bespoke stationery to save you a bit of stress
Not hard. I made mine - everything, invites, order of service, table plans, name cards, thank you cards. Bought card at paper mill, some cut out things at hobbycraft, some stampers and some ribbon and sat and did them at night. I didn't want something boring or mass produced.