You can use PuTTY to connect to your server and then use a text editor like vi or nano (I prefer nano myself) to edit the file.
Or use WinSCP (also free to download, see: http://winscp.net/eng/index.php) to edit the file. WinSCP is a windows program with a familiar "explorer" like interface that may be more to your liking.
Not at all. I use both. I use PuTTY when I need access to the command-line and WinSCP when I want to do file management (edit, copy, move etc.). You can even start PuTTY from the WinSCP toolbar if you have installed both (very handy).