Party Merge vs Customer Merge

Hi All

I have few questions around the Party merge vs customer merge process.

1. Is there single step/process to do both party merge and customer merge  instead of 2 steps process?

2  Can some one tell me step by step process for Party Merge/customer merge.

We have lot of duplicate parties and customer accounts (they are one to one) need to be cleaned up.

Any guidance/document would be helpful and appreciated

Thanks

Maran