yeah. so “not a concrete opinion about how to” applies to the entire subtree “accomplish it and make all the details work”. The “and” means both/all of its children/descendants.
If someone says “I don’t know how to accomplish X and do Y” they haven’t said they don’t know how to accomplish X. They don’t know how to accomplish X and/or don’t know how to do Y. If this is unclear, look at the logical truth table for “and”.
“opinion” (second one) is an appositive modifier for “opinion” (first one).
Here’s a simpler example with fewer irrelevant words. In “I want a red toy, not a blue toy.”, the phrase “not a blue toy” modifies the first “toy” by providing more information about it. Something similar came up recently at Grammar tree practice [AM] - #5 by Elliot @ActiveMind