Upgrades on Scott Speedster s50

I bought a 2012 Scott Speedster s50 a week ago as my first road bike. I think it was a really good deal. It was only $280 but the fork had a hole drilled in it through REI policy to make me replace it. So should I replace the fork with an aftermarket one or get an orginal scott fork. Also, The shifting was kind of rough. The left hand shifter which goes from the three big rings barely would shift to the largest ring so I just keep it on the small one. Is this a tuning issue or worth it to slowly upgrade to 105 components. Right now it has shimano sora. Sorry for not using correct terms or language with regards to bikes. Thanks for the help

Untitled by prenne5050, on Flickr

Untitled by prenne5050, on Flickr
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Regarding the gear change issue the level of kit (i.e sora) will not affect its function so it must need adjusting. This could be cable tension or it could be mech travel. Google gear set up or gear tuning.