1. A few general upgrade tips:
- study the release notes and documentation notes for each intermediate / final version you will upgrade through (e.g. 7.6.2 and 11g) to familiarise yourself with the differences.
- have a clear picture of any customizations you have, such as custom jars, modified OOTB elements, modified config files, any files in the webapp, etc. Each upgrade step may overwrite some of these.
- best to avoid using the sample sites' asset types for your own development, instead create your own asset types from scratch.
- take a complete backup (database and filesystem) prior to upgrade, so you can rollback if needed.
- if upgrade fails after deploying the cs.war, rollback and retry the upgrade with additional debugging (e.g. com.fatwire.logging.cs=DEBUG) to see more information in the futuretense.txt / sites.log during upgrade.
- if you have errors during upgrade that you can't solve, consult the Oracle Support knowledgebase if you have access (support.oracle.com).
- aim to finish on the most recent version, that way you can apply the most recent patches when they are released. For example we are up to 126.96.36.199.1 Patch 8 currently.
for 7.5 to 11g specifically:
- you need to upgrade from 7.5.5 to 7.6.2 to 11g
- the new cache framework "InCache" in 11g is significantly different from SystemPageCache in 7.5, study the Administrator guide to understand how to configure / tune the caches
- the Page assettype is changed in 11g, it is now a flex assettype.
- Insite Templating aka PageBuilder is gone in 11g, replaced with Slots mechanism, check the Administrator Guide to see how it is implemented.
2. If by migrating content you mean publishing, then that will necessarily involve an upgrade as you can't publish between different versions of Sites/CS. So for example if you have a 7.5.5 you can't publish into a fresh 11g, you need to upgrade the 7.5.5 to 11g before you can publish assets from it into another 11g.