I have bought 1TB 5400rpm Toshiba HDD and replace using traditional method. Torres thanks for your suggestion but I dint have enough resources to try your method. Anyway finally I have moved from 3.55 to 4.3. Decided to go for Rogero 4.3 V 2.5 since I don't go online and to keep everything simple. Steps done.
1. Backup existing HDD in a external usb.
2. Replaced the new HDD.
3. PS3 asked for firmware, flashed OFW3.55
4. Restore my backup to the new HDD.
5. Run Rogero 4.3 v 2.5 from xmb (tried recovery menu but didnt succeed. Also I dint do any QA flag)
6. Deleted existing Multiman and other homebrews from my back up.
7. Re-installed mutiman V18 full then v30 base and v30 update
8. Everything worked fine.
I was having double mind going for 1TB as some people said the system will be slow, but I took the words from Aziral and went for the maximum, I dont regret now, dont feel any major change to the speed of ps3. Thanks all I am playing Ninjs gaiden 3 Razors edge... with my new cfw. Some of my old PSN are not working but not bothered...