Total n00b question here, I did have a look for similar questions & answers first! I have a 2009 or 2010 Specialized Rockhopper SL with all Deore parts. The left shifter is broken. I can pay £23 for an exact replacement or £9 for the Acera. Both new and supplied with cable. Is the Acera compatible? Will it work? will I notice much difference in smoothness of changing? is the Acera very cheap and mostly plastic parts? also, does anyone have a decent link to a step by step guide of how to carry this job out, feed the cable through and make sure the chain, shifter indicators and the FD-M590 derailleur all end up in the right place?