General question about M2 Performance shop and my Transmission Rebuild
 

Does anyone know how reputable of a shop M2 Performance was? The car I bought has receipts showing a very fresh 5,000 mile transmission with no 5th gear grinds with my 5,000 mile engine and 5,000 mile t04s.

The reason I ask is because the receipt says they rebuilt the engine.

How long should it last and if it was the minimal rebuild what is the max hp / tq I can push safely?