[OT] sed command to add line after matching lines

[Dan Track]

Hi

I appreciate this is off-topic but I would be grateful for some help
on this. Basically,I want to add a few lines after matching a couple
of lines in a file using sed, can someone please tell me how to do
this.

Lines to match

server 10.33.45.3
server ldap.example.com
server orion

I want to comment these lines so they become:

# server 10.33.45.3
# server ldap.example.com
# server orion

Then append these lines after the commented lines

server fire.example.com
server earth.example.com
server space.example.com


So I should end up with:

# server 10.33.45.3
# server ldap.example.com
# server orion

server fire.example.com
server earth.example.com
server space.example.com

Please bear in mind there is a lot of other text in this file not just
the above and all the other text should remain untouched.

Thanks for you help in advance.
Dan