How hard is it to change a starter in a 340 Duster?

I got the starter on and it fixed my problem. I was not able to crank it using the key though. A friend showed me a way to crank it from under the hood. I used a long wire and put one end on the positive terminal and the other on a wire that I’m guessing went to the starter. It still did not crank, but it was trying to. The starter works now, but the old one did not. I think I need to set the timing because it tries to crank, but it’s just making loud banging noises from the engine and the distributor shakes a little.
Your probably talking about a backfire noise. May be a timing issue. Can you email me a short video of it trying to start?