Gaskets and Rusted Exhaust System - Bother to fix?

Hello - I have a 1999 Infiniti QX4 (130k miles) and have two questions -

1 – First mechanic (dealership) assessed my complaint of an antifreeze smell at higher speeds and a check engine light warning as a leaking power steering rack and suggested replacement. Second mechanic (respected neighborhood guy) said he thinks I have leaking gaskets or possibly a cracked engine, but can’t tell until they take the whole thing apart for thousands of dollars and that they might discover I need a new engine so it may not be worth it even to investigate. I love the car and can’t afford a new one right now, so would like to just keep it running as long as I can. I read in the forums about using a type of sealant for gasket leaks - is that a viable option here? Also, any idea how long the car will last if I don’t do the repairs or other thoughts on extending its life?

2 - Same car, the exhaust system is rusted out and the muffler is no longer attached to the system. Given the above issue, are there actions I could take to keep the car running without replacing the whole system for a car that may soon die? I’ll have to do a smog test in April and realize it may not pass if I take shortcuts but would like to know my options.

Thanks so much for any help you can offer!

I have leaking gaskets

at higher speedsI either have leaking gaskets or possibly a cracked engine (smell of antifreeze when driving at high speeds)that they can’t really tell until they spend a lot of money to go in there and I might spend all that and need a new engine. I read