There is a a product that works with FCP 7 and FCPX as well as your FCS assets (CatDV Production Management). I saw a product demo of the product last year. I was pretty impressed with how well it worked and how easy it was to set-up. Here's a link to the FCS migration process to CatDV.
Hope this helps.
You can switch to Premiere Pro pretty easily - especially if it's already installed. Ideally, it should be CS5 or newer.
Is your workflow tape or tapeless? And, is your source footage Apple ProRes or Apple Intermediate Codec?
You can continue to follow your FCP workflow and just substitute Premiere Pro for FCP, but you might want to switch to a Premiere Pro workflow if your footage is almost always the same file based format (like always DVCProHD or always MTS). I try to keep the best of what FCP did and make that work in Premiere Pro, including using Apple ProRes.
Your FCP project files can be saved from FCP7 as XML and then opened in Prmeire Pro. Most of what you were doing in FCP is preserved.
The main thing I miss while cutting in Premiere Pro are the range of keyboard shortcuts. There are times in Premiere Pro where you have to click. Creating and editing markers is a good example of this. In FCP7, you just pressed m and pressed m again. In Premiere Pro, you can place the marker with a shortcut, but you have to click to edit it. I'm hoping this will change as Adobe continues to make Premiere Pro what FCP8 would have been.
Oh, one might also miss being able to have more than one project file open at a time.