You know i cannot use URL aliases

One thing i must ask you :
I saw that SEF is overwriting the sefRelToAbs function and includes/sef.php is not used anymore so i think it`s impossible for me to add SEF to my links.
Now, can you point me to the right direction where i can read about sef_ext
or can you tell me in what cases your script loads sef_ext files (i know it should be uploaded into the component directory). Isnt possible to hack this, i mean a backdoor or something to make SEF reads joomla content.
( if it`s possible i`ll learn and write my own )
I hope this make sense.
Thank you again in advance.