I'd suggest http://breis.focloir.ie/en/fuaim/ over forvo, if you want recordings. Forvo is crowd-sourced and the pronunciations are not always right. The link I've given has professionally recorded pronunications from native speakers of all 3 major dialects. Its only shortcoming is that it only has dictionary headwords.
www.abair.tcd.ie is also good, and will give you pronunciations for every word; however, it's synthesized.
fear is "man"
fir is "men"
maith is "good"
fearr is "best"
There is no relationship between "fear" and "fearr". It's just a coincidence.
Here is a list of all of the prepositional pronouns.
le is "with",
leat is "with you".
Literally, the sentence breaks down as "Is best with you stew", or "Stew is best with you" or "You prefer stew".
"Is maith leat stobhach" breaks down as "Is good with you stew" or "Stew is good with you" or "You like stew".