yes to the manifold, I bought mine at around 84k miles, it was cracked already by then. symptoms? you'll hear it, pop the hood with it running and listen.

Doing a lot of highway miles, and you dont want to get stranded on the side of the road,....... yet you still want to wait another 20k miles on the belts? yes, your miles are low, but I think the time frame for changing it was 105k OR 7 years. If it were me, I would rather change it now and know its going to be good for the next 7 years instead of taking the chance, just my 2 cents though.. .. .. ..