Flavio,
You might watch this video on how to rebuild a rotary so you can see what's involved.
http://www.youtube.com/watch?v=ijJeU...ayer_embedded#!
The first part is doing the seals.
Then you can pull yours, take it apart and then see what, if any, parts you'll need to replace.
There are folks like Karack @ rotaryevolution.net or Kevin @ RotaryResurrection.com who can rebuild the engine for you if you feel it is beyond your ability or level of interest.
If you decide to get a JDM engine to replace yours I'd contact Japan2LA as he has an excellent reputation for used engines where most of the importers dont understand rotaries and can be less than ethical.
Good luck!