I purchased a used 583 today, it came off of a kitfox about a year ago and has about 300 hrs on it.

I am looking for advice on this engine and have some questions.

#1 What problems should I look for with a 300 hr engine that has been sitting for possibly over a year?

#2 How many hrs can you get out of a 583 ?

#3 I have mounts for a 503 will the 583 bolt up or will I need new ones?

Any other advice would be welcome too
Thanks