Wow... 2.3.2 is pretty old
The lastest package for 1.0 is 2.4.6 and that is almost 2 years old itself. You'll need an active DT Register license. Then download the latest package. It will have everything you need as 1.0 and 1.5 packages are included. From the state you are at, you should do this:
1) Upgrade to 2.4.6 using the readme file instructions included.
2) Upgrade to 2.6.9, again following instructions.
3) Upgrade to 2.7.3, following instructions.
You should backup your existing database, then make another backup at each upgrade point... just to be safe. Moving from 2.3 to 2.7 is MASSIVE.. but doable. If you can do without your old 2.3 data, it would be easier to just wipe it out and get a clean install of 2.7 in Joomla 1.5. If you need to keep it... fine, just follow the upgrading instructions. Thanks.