You can import using default Magento import method or use Dataflow, which is also available out-of-the-box. However, you need to stick to strict requirements Magentio itself has to import file columns and information in them. You can check requirements here -
If you need to export only some products and automatically do modifications - let’s say re-calculate price (adding 5% mark-up) automatically without the necessity to do it manually in the file, you will need some extensions or scripts.
In case you are interested, there is 14-days free and fully-functional version of Store Manager for Magento application:
Using it you can export products from definite manufacture and import the file back adding price mark-up on-the-fly right in the process of import.
Moreover, there is even faster way to to it - filter out goods by manufacturer , right-click and set 5% price increasing for selected goods with Multi-Editor option of Store Manager.
In any case, you can download the software and give it a try.