A question on AWS RDS Multi-AZ downtime when changing the Instance type

Question

I have an RDS Database serving a production application.

The RDS DB is a db.m3.large and is Multi-AZ Instance Deployment. (Role is "Instance" in the console).

I've been informed by AWS that I have to migrate my Database from an M3 instance to one of the newer types this time next month. This is the first time I have had to touch this Database on the hardware side for quite a while so I would like some validation on my understanding on how best to approach this.

I am aware there is documentation but its a bit vague and I would like a statement in laymans terms.

My current approach/understanding on how to handle this would be:

1. I modify the instance type
2. While the instance type is modifed, failover occurs and the traffic is redirected to a standby instance to handle traffic while the changes are modified
3. The failover will occur from between 60-120 seconds, so that would be the expected amount of downtime.
4. Once the job is done, the traffic is redirected to original primary instance