Feel free to commit to your sandbox whenever you like without checking with me. Just right click the topmost folder and choose SVN Commit (still always best to do svn update before committing).
Probably best for now just to let me handle merging to trunk since I am also working from a sandbox and may possibly have conflicting changes between us. But you will need to learn to do merging because there will be a need to merge trunk to your sandbox to get my changes.
The basic steps when merging from one branch to another I will explain in the context of what I do to merge my changes from my sandbox to trunk.
First I have a local copy of trunk checked out in a different folder than my sandbox.
I do svn update on this copy of trunk to make sure it is up to the latest revision.
Then to merge I right click the topmost folder of my local trunk and choose TortoiseSVN > merge which brings up a dialog.
Its important to check Head Revision at the top then ucheck the checkbox that says "Use From:"..
Note that in this example I am merging from trunk to my sandbox which may seem counter intuitive but what it does is make my local copy of trunk the same as my sandbox. This can take about an hour. Once its done I simply commit trunk and now it is the same as my sandbox. Its all very simple with very few committers but we will need to be in communication to avoid problems. When you are ready to move your changes into trunk let me know what folders have changes as it is possible to merge folders at a time instead of the whole branch like in the example above. Sometimes after a merge there can be merge conflicts which must be resolved in the local copy before it can be committed. In the beginning I will probably merge folder from your sandbox into mine and then merge my changes and yours together into trunk. After which you would want to merge your sandbox (from your sandbox to trunk) which would update your local copy of your sandbox to be the same as trunk then you commit and your sandbox in the repository will match trunk.
Webstore needs to be setup similar to what I did in your Poll feature so it copies an application folder beneath the web/Setup/applications containing versioned setup/upgrade scripts. Then when you need to run a script to update the schema or add/modify procs you just add a new version script in SchemUpgeadScripts/dbname folder for your app and then visit the setup/Default.aspx page and it will run the script for you.
I've been intending to do that myself but might be a good thing for you to do to get a better understanding of the setup/upgrade system.