I tend to believe in full fluid exchanges but this is quite some miles. I'd be tempted to do a drain and fill a couple of times, then a full flush. It's only a couple extra gallons to do that and a bit of time (over a full exchange that is).
Pretty sure this is a strainer, not filter. But the magnets should be cleaned anyhow. 50/50 coin toss as to if it really matters to clean the magnets, whatever it has shed, it shed long ago and got caught on those magnets--is it worth messing with the gasket (and breaking any pan bolts) to clean that? I think I'd skip that step, just drain and fill a couple of times, then full flush down the road.