Upgrade symfony from 1.0.0-rc2 to 1.4

[nwbrd]

Hello All,

We are running one website which is built up on Symfony 1.0.0-rc2 version. The requirement is to upgrade up to Symfony 1.4
We are NOT using PEAR installation, symfony classes resides in \lib\symfony directory.
We are using just two plugins in \lib\plugins 1. sfFPDFPlugin and 2. sfThumbnailPlugin

I have never before done such up-gradation, so I would request here any experienced to guide me 'proper' way to upgrade symfony upto 1.4. Any kind of help in this regard will be highly appreciated.

Regards,
Nwbrd.