Apparently the shower door in the later 23's (I had a 2011), were problematic, as AS switched vendors in 2012, I think.
Now when you say slider, I'm assuming you're referring to the SWEEP that is in the threshold of the shower enclosure.
If that's the case, the only way you'll be able to replace that sweep it to remove the threshold in order the slide the sweep into the slot that holds it.
And yes, while the threshold is held in place by two screws, there's one hell of a lot of silicone under it (which I think, is one of the tell tales of water problems that caused AS to switch vendors in the first place).
In removing the threshold, be careful (and patient) not to bend said threshold.