Hi Paulette--
The easiest thing is to delete the old content and insert the new. Something like this should do the trick:
function replaceContent(oid, newContent) {
# where oid is the oid you want to modify, and newContent is a markup string you want to put there instead of what's there now
oid_delete(oid, 0x2); # 0x2 flag = delete element content, but preserve tags
goto_oid(oid);
insert(newContent);
}
--Clay