The clutch in my beloved 2003 RSX-S has started to feel mushy & will, at times, stick when engaged. I've also had issues putting it in gear.?

Check the clutch slave cylinder for a wet dust boot. Once there is fluid on the dust boot there is air in the hydraulic system causing the mushy pedal.

The clutch master cylinder can also leak but 80% of the time the slave cylinder is the leaker. Fix it before you ruin the gears in the tranny.

A question mark does not a question make.

The transmission may need to come out to fix this. If the pilot bearing in the flywheel binds up it will drag the transmission mainshaft so it continues to try to spin when the clutch is pushed in and makes shifting difficult, often grinding the gears. There's a chance the problem may be simpler; If the clutch does not full disengage due to low fluid or air in the clutch cylinder, it will be hard to shift. Check that before tearing into any disassembly.

So what's the question, because I don't see one here.

probably has a hydraulically-actuated clutch, make sure there's enough oil in the cylinder ........................

Taking it to the dealership would be cost prohibitive & I'm skeptical of fix-it shops. Thanks!