Well I guess it might be a good idea to wait for your supervisor and make this update slowly but you know not mess something up, especially regarding back ups etc. But the release notes that I gave you should help you (and your supervisor) to make it without problems.
As for large files upload, this will need to be adjusted in php.ini file, you can find more details here: How do I upload files bigger than 2MB / How can I increase the upload file size limit?
Edit, well something is definitely missing there, I’ll tell you more once you will export it - but since now you got this error when you try to export layout, we will wait till you guys update CMS to 1.7.4