Maintenance Replication servers (no replies)

I have setup Master-Slave setup for replication and now i want to do some maintenance on my master server, so i wanted to know what steps i have to take on my servers
So i have Server A (Master ) and Server B (Slave) and i have to upgrade the memory on server A....so if i just stop slave will that be ok, while the master server is rebooted?

Will i have to rebuild my slave once the master is up?
Will it be out of sync?

Please help me