Mason,
Begin reading the Latin America threads on HUBB and elsewhere and keep reading. It's all here and more.

You're backpacking experience will serve you well, stick to that style as much as you can. A light weight bike is easier/safer to ride. Realize you can buy nearly anything you need down the road. So bring MONEY, twice what you think you need.

Bring a camera and buy a local cell phone once in Mexico.

Depending on which bike you have, you probably will not need to carry a gas can. You need to have range of 150 miles minimum. Starting with brand new touring tires should get you to Guatemala or El Salvador where you can buy NEW tires.

Start your ride with :
1. New tires
2. New Battery
3. New chain and sprockets
4. Complete service on bike, checking everything twice.

Learn your bike.

If the bike is in good shape you now should be ready to ride 12,000 miles without doing much to the bike. That should get you to Costa Rica and back.

If you've never done a bike trip before I would think about doing some weekend trips locally. This will get you used to spending 10 hours a day on the bike and you can figure out how to pack up the bike and carrry your stuff. Who knows, you might hate it and decide not to go by bike?

May/June your biggest problem will be heat, humidity and possibly rain further South in sub tropical lowlands.

Good mesh gear a must. Get your miles done early in AM, by 2 pm you should be done. As a novice I would NOT ride at night, even though with cooler temps it is tempting. Don't do it.

Plan riding days and set a destination for the day. Keep it short at first, like 150 to 200 miles max. Pick a town and get there. As you get better, you can extend your riding days. Take your time getting used to crazy driving styles down there, good defensive driving skills a must.

Tools. Yes. Build a good lightweight tool kit and make sure you can actually work on the bike with the tools you have. Bring tire repair stuff too, spare tubes or plugs and glue if running tubeless.

It's all covered here 50 times over. Start reading/searching.

Have fun!