I don't know why people are so hesitant to call the dealers or parts department for questions like availablity of an item. they will know more than us. but if you're not going to pick up the phone and call, just no that none of us has heard of a remote start as oem for models before 2006. 2006 may still not have it.
Like my dad, you're a huge fan of oem stuff. as far as alarms go, it's definitely less stuff for more money. you can get a state of the art james bond alarm for $600. Autostart on a regular alarm for $350-500 depending on where you live. A simple alarm will be much less. no one will ever see under the hood to notice an aftermarket part. dealers expect to see aftermarket alarms and will not be surprised to see one installed. the resale value you'll get on a car with a stock alarm vs aftermarket is negligible. That price depends on so many other factors that override your alarm issue.
be aware that some alarm installers have gained the reputation of copying down your address, installing your alarm, coming to your house in the middle of the night and breaking into your car. it happpens, so definitely take time to find a trusted installer. no one knows where you live b/c you haven't disclosed it in your profile, so we can't help you recommend one.