How can I change the position of the review block in the sidebar?
The order in which blocks are being displayed in sidebars depends on the values in the layout update (/app/design/frontend/base/default/layout/et_latestreviews.xml).
By default review blocks are displayed last (after="-"). If you want to change that order and place that block before or after some specific block, you can replace the "-" with the name of the block you want relate to (e.g. "catalog.leftnav").
If you want the review block to be displayed first, you should use before="-".
The process of displaying blocks in the sidebar depends on the way blocks were added and what position values these blocks have. If several blocks need to be added last, the real order of these blocks will depend on the order that Magento is reading the layout updates.