Steps for creating a slightly modified package and uploading it in a PPA?

So, are there some simple steps to take for this task?

It is only "simple" if you start with a package that exists in the Ubuntu or Debian repositories. Here's an outline:

1. Use apt-get source to download the sources/diffs for the package and apply them.
2. Go in inside the directory, apply your patches/make your changes.
3. Use dch to update the Changelog with what you modded and "name" your custom version (usually a `ppa1~series1 type designation).
4. Run debuild -S -sd or debuild -S -sa, depending on whether your original package sources exist in the target series repository or not.
5. gpg-sign the package when prompted (the key'll need to be registered on Launchpad).
6. Use dput to upload the xxxxxx.changes file to Launchpad, which will also include the diffs and maybe the source depending on what debuild switches you built
7. Relax and keep checking your PPA for the build status/updates.

If you are backporting or using bleeding-edge Debian Sid sources, etc., it's a good idea to set up a chroot and between step 3 and 4, run dpkg-buildpackage -us -uc to nip any dependency issues in the bud.

Why not go one step further and share your bug fix with all other Ubuntu users?

The packaging guide has a fairly straightforward howto on the topic. You don't have to "read all the docs".