You really should patch ArmA up to 1.14 if you want to use ACE.
ACE should autoinstall into it's own folder in the modfolder style. So be sure to include -mod=@ACE on your startup or better yet use one the the ArmA launchers to manage your mods for you.
ACE is aimed more at multiplayer. You can use it for solo, but some of the SP missions that come with ArmA are not totally compatible with ACE - the helo missions in particular don't like ACE's vehicle startup sequence. So do concider either crafting your own SP missions or getting ones that are ACE-compatable from sites like this one.
This post was edited by Foxhound (2009-06-30 06:29, ago)