Its pretty common for the old sequoias and land cruisers to have leaking manifolds.
The only symptom is the car with have an exhaust leak on cold starts, This may be something you are use to, and its not a big deal, nor a safety concern.
I would just ignore the recommendation. Its not a necessary investment, especially, if its so minor, you are not even noticing it.
No, none at all. worst case is they leak so much, they may throw a check engine light. because a faulty oxygen sensor reading.
However, I've never seen it happen.
Warranty time is 10 hrs, however, with the correct tools, its not that difficult.
12hrs is a bit excessive.
Anyone who has done them before, knows that 10hrs is more than enough.
Toyota parts prices are all the same.
When I go to work tomorrow, I can get you a more exact price including parts.
Then you can call around and shop it.
To be honest, I would just leave it alone, its not worth the investment.
At my dealer the cost would be. $1525.00 + tax
Parts are $466.00, the rest is labor