With MySQL Replication, what level of resilience is possible?
A lot of the questions you are asking are predicated by use of master-slave replication. Life's a lot simpler if you use master-master replication; master-slave requires detection of a failure on the master and promotion of the slave. While this can be automated to some extent, you also need to think about how you implement reinstating the master.

Regarding data-loss: get over it. Although there are various approaches implemented in different products, even moving transaction control outside of the database cluster, there is still a possibility of losing data. The only practical solution is to design your system so that its possible to identify failed operations (which is good practice as such losses are more often caused by software bugs than system crashes).

Regarding the details of how you implement the system - a lot depends on the OS you are running on, the impact of downtime, the architecture of the application, the nauture of the network connecting the nodes in the application....lots of information which you've not provided. 

There are some useful links here