There are plenty of threads/posts on Office Apps, so just try a search first (for myself I'm using iWorks, i.e. Pages, Numbers, & Keynote) - there are some excellent summary threads discussing the various options.
If you have problems findings these threads, then post back to your thread - good luck!
Personally I like Quickoffice, i have a few office apps but this is the one that I use the most. I find that the pricing is good so that I can afford to have a few on my iPad and then I get to choose the best for each situation.
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/