depends what you mean by the "standard" version.
originally it was released as a "standard" version and a "deluxe" version. the deluxe has a couple more planes and several more missions. for example, the goose and the maul are only AI in the standard version. you can't fly them.
if you are talking about currently having only fsx sp2, and not acceleration as the "standard version", then that is another matter. you can buy acceleration and just add it to your already installed fsx. that's what i did. you'd gain nothing important by getting the gold version. it's just fsx and acceleration all in one package.
that said, un-installing fsx and re-installing it isn't that hard unless you have a bunch of cfg tweaks, add-on terrain, weather, etc. i should know, i've already un-installed it and re-installed it 5 times.