I just left a post in THIS THREAD referring to several excellent threads that discuss business/office apps - take a look!
For myself, I am using Apple's iWorks (Pages, Numbers, & Keynote which simulate Word, Excel, & PowerPoint); each is $10, so not a major investment - these programs in NO way match the dedicated MS programs on a standard computer, so don't expect an identical performance if you chose to use these apps - read the linked reviews and define your needs - good luck in your selection(s)!
I use the Apple iWork programmes but find that Quickoffice Pro HD has performed best for me......although I get sent quite a lot of formatted excel files.
There is lots of good advice and info on here plus plenty of members all too willing to help with any problems.
Remember, search is your friend. If you can't find the answer you need and you post a question then give as much info as you can to help members help you i.e. iPad 1 or 2, iOS version and name of app if the problem is with a specific app........and please don't forget to read the rules http://www.ipadforums.net/forum-rules-help-info/2119-forum-rules-everybody-please-read.html
You can download the manual for your iPad here http://support.apple.com/manuals/ and in iBooks search for "iPad user guide for" and you will find free comprehensive manuals for both iOS 4 and 5.
If you have other Apple products or are interested in other Apple kit then why not join our sister forum too at http://www.appleforums.net/