My wife and I are looking at purchasing a new 09 Accent Hatchback. We looked at one with power doors, windows, and keyless entry from the factory, and we are looking at one without those power extras. The one without the extras is about $1500 less. The only feature she really wants is power locks /w keyless entry, but I don't know if that really warrants the extra money. If we decide that we would want them later, how hard is it to install, does it void the warranty, and how would I go about it? Thanks in advance.