1998 SAAB 9-5 9-5 turbo breakdown is it possible?

Hey guys just wanted to ask you guys a question and hope there is someone who can give me an answer.

I am one of those people who doesnt trust mechanics 100%. I mean they can rip you off if they see you dont know the stuff. So here is the story

I bought this saab 9-5 (98 model with 140.000 kms) and it was all good till about a month ago. First I had this oil lamp blinking sometimes, I first tought its oil level then I checked and it was ok. Then I changed the oil and oil filter and went for a drive when I heard some noise from the engine. Sounded like something was scratching of something and I felt its loosing the power. It was just a short drive around the block, a few streets. And when I came back and stopped I saw a big cloud of smoke behind me, I thought the car was on fire and I jumped out. I started the engine a couple of times after that when a friend came to check it but I wasnt driving it.

So I brought it to a mechanic with a tow-truck and he said the turbo was gone. He wanted 1700AU$ for a new turbo and another 500AU$ to change it. I bought it from England for 700$AU and when he changed it he called me saying I have a problem with the engine, I need to change timing belt or something something is broken some broken screws are inside. And when turbo exploded a lot of it went into the exhaust I might need to change the exhaust as well. And he says its gonna cost me another 2000 AU$ at least coz its a big job he needs to take the engine out.

So just wandering if u guys think this is possible, that it just breaks that much so suddenly or he just see that he can get some more money.

Im sorry if my English wasn't perfect or if it was to long but think im just gonna feel better if I make sure im not paying for something I shouldn't.

Thanks