Set the park brake, shift into 3rd gear, hold the foot brake, and rev the engine while releasing the clutch pedal. Yes, it takes 3 feet and do this somewhat quickly.
The engine should stall out and die. If it does not the clutch is slipping.
How long it will last depends on how bad the situation is.
It's quite possible for a clutch to give before 46k miles. It all depends on the driver and the type of use it gets. A lot of city driving can speed up wear on the clutch.
The price could be fair depending on the locale, etc. Some areas of the country have much higher labor rates. (East and West coasts are higher than the mid-section) Factory OEM parts will usually be more expensive also.
If you need a clutch, price this around at a few independents first. You could possibly save a few bucks by going that route.
(Just a word about the guide sleeve which mounts the throw-out bearing. The inside of that sleeve, which is made of steel, has a machined grease groove on the inside. The edges of this groove are knife sharp. The snout of the transmission is aluminum (soft metal) and it's possible for the knife edges to dig into the aluminum. This can cause a dragging clutch; a.k.a., premature wear. We had a Subaru even towed in once in which the clutch locked completely in the disengaged position due to this. I've always machined the sharp edges off and greased that groove before installation. You would be surprised at how many Subaru techs are not even aware of this. I've got half a dozen permanent scars on my hands due to guide sleeve and transmission case half cuts.) Hope some of that helps anyway.