What can I expect after removing an abscess from a previously done root canal on the same tooth?

It may heal. A well sealed root canal with a proper restoration will generally heal. The outcome depends on several factors including the bacteria present, whether the natural tooth anatomy was respected and the ability of your body to heal. Success rates are in the mid 80's in the absence of complications.
Trouble-free years. Re-treating previously-endodontically-treated teeth is more common than you may think. Sometimes even the best textbook root canals have issues over the years. Endodontically-retreating a tooth attempts to remove any debris and/or bacteria that cause issues--an abscess in your case. Once the offending material has been removed and the tooth filled, the tissue surrounding the tooth should heal.
Ask the dentist. You may need an implant, or it may be possible to place a crown if the infection has entirely cleared. But must be certain that there is no underlying chronic bone involvement.