I'm new to the forum, recently bought a Gen3 2000 3.5 V6 5-door GLS

Took it to SupaQuick today to have the battery changed and they told me I'll have to replace the exhaurst branches and eventually the manifold as well. (I assume they're talking about the outlet manifold)
I'm not very good at mechanics, what should I do - get 2nd opinion or where do I start fixing this problem. (they quoted me about R 20k to replace the branches and manifold)
The car only has 88000km on clock, but did a lot of city (traffic) driving in Joburg. I suspect this is wear and tear?
Any advice will be highly appreciated - thanks!