How important is this overall? Is it a make or break sort of decision, hit or miss, or just perhaps a minor modifier?

I tend to have one or two jockeys I try to use (and am often thrown by their lack of being available when they don't seem to be in the race I'm selecting, but ARE at that track for another of my horses).

I'm also not clear on whether it's possible to essentially hire a jockey or two to be my automatic lock-in so that I don't even need to select them and can depend on their feedback.

For now I started by picking jockeys without looking at their cost and only looking at their win percentages and going with the top winners. Now that I've been heavily choosing them (and winning far more than the other trainers) I MAY be artificially creating my own bias here by boosting their stats and then only continuing to select them based on those same stats (if that makes sense). Then again, perhaps they're racing so much that my meager runs are not really having much impact.

I also know I should be considering weight here, but so far none of them seem to be hampering my stable (though I can't be 100% sure of that).

Lastly, how likely is it that a jockey will tell you information that's just patently, unquestionably 180 degrees, dead wrong, and possibly doing it most of the time?

Thanks....

You can "retain" a jockey so he will be the default rider for your stable.

Click on the "Jockeys" tab then click on "Apprentices".
In there there are 2 lists...one for apprentices and one for jockeys.
Select the jockey you want and then hire.

Is that in every mode of play? I don't see any "Hire" option. I see the jockey and apprentice lists, but selecting them just brings up a summary of their information with no Hire button.

Not sure about all modes of play.
I am in "Owner/Trainer" mode.

I just click "jockeys"....then click the button "Apprentices" and i get the screen below.
I select the jockey i want and you will see the "Retain" button on the lower part of image.