The Android 2.3 upgrade for the Ace has to come from Samsung through official channels — i.e. Samsung’s own OTA (over the air) update.
Before the official update is out, if you try to root the phone or install another version of 2.3 — the warranty will be voided. In case your phone is bricked (software damage) during the process, it will not be repaired under warranty.
To check whether the official update for the Ace is available — look in the settings for ‘software update’ (in the about phone section).
Sometimes, software updates are also delivered via Kies (Samsung’s PC software). If you don’t have Kies, download and install it from http://www.samsung.com (support section ), and then connect the phone to the PC to check for updates.