MacBook Pro trackpad sticking, acting strange

Question

My MacBook Pro Mid 2012's trackpad has started making clicking sounds when I click on it (it never used to be this audible) and feels as if somehow some kind of sticky liquid has gained access to it -- however, since I am the sole owner and user and have never, ever spilled any liquid on or near it, I can't figure out why this has become so.
I've had other Mac laptops where some kind of liquid HAD been spilled on it, and the feeling is similar, but not nearly as pronounced.
I don't know quite how to explain it, but if I very, very gently press down on it with my thumb, there is sort of a "pre-click" before it actually clicks. This is, now that I've tried it a couple of times, very noticeable.
Furthermore, sometimes when I'm scrolling through a Web page, not pressing down at all, it suddenly starts "selecting" blocks of text, and also occasionally goes to a link without my having clicked anywhere.
Other times, I try to scroll with the two-fingered method (lightly holding two fingers together and sweeping them downwards without any downwards pressure) it doesn't scroll at all.
It's definitely not normal behaviour -- I've had Mac laptops since the PowerBook 5300ce and I know my trackpads!
I know you're going to say I must have inadvertently deposited some liquid on it at some time and just not noticed, but I can swear this is not the case.
At any rate, are there any measures I can take by myself to try to clean underneath it without taking the whole thing apart or taking it in and paying $200 for someone to take a look at it?
Perhaps I should give it up and get a mouse for it . . .

Answer 1

"Taking it apart" is not an option for just cleaning the trackpad in these models. The trackpad and keyboard are the first components bonded into the chassis, and EVERYTHING else goes on top, hence would require a total disassembly. 10/10 degree of difficulty and high probability of gaining a fancy paperweight or doorstop afterwards.  If 2012, then it is almost certainly within the one-year base warranty period: let Apple deal with the problem.
That being said and in lieu of a visit to the Store, note that the trackpad pivots down along the front edge. Hence there is a tiny gap between it and the chassis to allow movement. Examine that airgap very carefully with a strong light and a magnifier. Two things to look for: any sticky fluid that may have trickled down or mechanical obstruction impeding free movement. Dirt, crumbs and such can work themselves in there and do the trick. If found, try to work it out with a can of compressed air; a "duster", if you will., maybe helped with a very fine brush. If that doesn't work, some success has been reported by using very high quality spray electronic parts cleaner, non-residual, sprayed with the Mac UPSIDE DOWN so none trickles down into the guts. But I still recommend a trip to the Store first.
And you may give serious consideration to buying AppleCare and extending the warranty coverage for an additional two years. Just remember it has to be bought and activated BEFORE the base warranty runs out.