This is what I can tell you in one go.
For upgrade to Halogen 100/90 watt here are the details:
Step 1: Purchase bulbs and a wiring kit. The wiring kit helps you to get a clean job done. There is no cutting of wires and voiding of warranty. Cost of both could be around 1000. Wiring kit: Roots and bulbs like phillips rallyee or any reputed 100/90watt lamp. Install will take max half hour.
Step 2: Remove stock bulbs and holder. Connect one of the default holders to a dedicated pin of the wiring kit.
Step 3: Install the new bulbs and lock them in place. attach the holders of the wiring kit to the bulbs.
Step 4: There are two wires of the kit which are to be connected to the battery. Connect them respectively.
Make sure all connections are proper and switch on the bulbs. This completes the job! the wiring kit consists of all the necessary connectors and relay to make your job easier. It uses the old holder as a signal cable, which contols a relay. The relay acts as a switch which provides a dedicated line to the bulbs from the battery. This hence doesn overload your default wiring.
Hope this info is enough. However you can search for videos and get to know more.
This might not be fully accurate but this is the overview of the work that is done. Work without a wiring kit will involve an electricians brain to route the wires. Hence a wiring kit is the best option.
Info on HIDs for beginners:
Hids are high intensity discharge lamps. A HID kit consists of a Ballast, wiring kit(same as above), and a pair of lamps. The light is generated not by a filament but with the help of an electric ark. It consumes 35 or 55 watts of power but gives an excellent output.
Usage of HID kit requires more work than a halogen. The ballast provides the working voltage for the bulbs to run. A branded kit costs about 10k and will be reliable than a cheap chinese kit. Unlike a halogen lamp, it doesnt have two filament for high and low beam. However, the bulb or a cutoff will move in according to the beam. HIDs are not so good on the highway so hence it is recommended for a car having separate lamps for high and low.
Where there is a wheel, there is a way!