Is it possible to upgrade internal HD on 2nd Gen Blackbook??

That is not true. Currently the biggest easily available is a 250 GB drive. These are very good instructions on How to Upgrade Your MacBook's Hard Drive. 320 GB drives are coming out but they are hard to get at the moment.

Here are the Apple Apples DIY hard drive replacement instructions.
The only step they left out is the need for a number 8 *Torx Driver* to swap a shield from the old drive to the new. Apples DIY Warranty Info

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This is the drive http://www.westerndigital.com/en/products/Products.asp?DriveID=377

The 250 GB drives were like this when they first came out and they are better priced and easy to find now. You can check here OWC MacBook Ram and Hard drives for ideas of what can be bought easily. You may have comparable stores in australia. One other thing is size restraints. Below are the sizes you need to watch for. There are some drives that are 13mm high. They won't fit. It has to be 9.5 mm.

English
Height: 0.374 ±0.008 inch
Length: 3.94 ±0.010 inch
Width: 2.75 ±0.010 inch
Weight: 0.26 Pounds (±0.10 lb)

Metric
Height: 9.5 ±0.20 mm
Length: 100.2 ±0.25 mm
Width: 69.85 ±0.25 mm
Weight: 0.117 kg (± 0.082 kg)

I figure 2 to 4 months and they will be easier to get. Right now they are very hard to find. Thanks for the it is appreciated.