Left clickers not working

How old is the 'left clicker' aka mouse button?  It may have just been used too much if it's older.  Does it feel the same as you expect the button to feel?  If it's sticking or not 'bouncy' then you've likely got something broken inside.  Compare it to how the right button feels when you (try to) click them.

 

Try looking at the manuals on the support page.  There's one that tells you how to (dis)assemble the button and replace it with another one.  Dell is very friendly with giving information on their site to people trying to fix their gear.  You can get pieces from people who 'part out' their broken laptops, at decent prices.  If you've not worked on laptops before, and especially if you've not got lots of electronics repair experience, this might not be the job for you.  Of course, it's obvious that it's the nature of a community site with free advice, that you're the one taking all the risks if you break it further.  I still try to give you too bad/unsafe of advice.  ;)

 

Your best bet is to make sure that it's not possible to fix it without spare parts, before purchasing random pieces of kit.