Big end bearings

I bought this car from a garage and have a 6 month warranty on it. They drove it up to my house on the 26th of July as my insurance would not cover it until the 18th of August which they knew. I drove it a week and when I went over 3000 revs or even changing gear I heard a noise. Brought it back in last Wednesday and they said it's a bearing so have to take the engine apart ( I think the big end bearing) they said it's a huge job and will take between two weeks to a month (this is a Honda/Subaru dealership) now I know they said there was an oil leak that they fixed before they sold it to me. Also I noticed some serious heat coming from the engine. Now the oil hasn't gone down at all but I can only wonder has the car been driven into the ground which is why the bearings need doing and it's over heating. What my question is is that if those bearings went - 1/ am I entitled to ask for a new second hand low mileage engine? 2/ am I entitled to an extension on my warranty as the problem was there when I test drove it before buying? 3/ should more things be replaced like the oil pump etc? As this will only be a slippery slope on non stop problems?
I think because I'm a girl and young they think I don't know my cars but I know when there is a problem and I know when one issue becomes 10 issues just because of one thing. Basically I have lost all trust in them and have forked out thousands for a new car in "perfect" condition. But they knew there was a problem with it bringing it up to me (they couldn't have not known) I am just unsure of what to do or what I'm entitled to and am afraid of being ripped off.
I'm desperate at this stage for some advice. I'm afraid they will do a shit job on it thinking I won't notice and I probably won't by the time my warranty is up.
Absolutely any advice on what to do would be so greatly Appreciated you have no idea.
Thanks in advance
Jessica