Firewall Security

I need help… I am an ALL in one Admin at the small company I work for. We are just now getting DSL for our internet connection.. what my question is what is recommended for firewall support for my company.. I don’t want to make the DSL connection live until I know I am atleast somewhat protected.. yes I know I can’t be 100% protected but I do need to know what i need. I am new in the Sys Admin field but have been a Tech for 4 years…so any help will do…
Thanks