Bicycle Tutor

I have a 1989 Panasonic steel frame road bike, 7 speed. Is it possible to replace the cassette with a 9 speed on my existing wheel? Or do I need to replace the wheel in order to get the 9 speed cassette, and is this even possible on this old of frame? If this is possible, I would eventually like to update as many components as compatible. I am getting weary of downtube shifting.

I'm not 100% but I am pretty sure something fomr the 80's would be a freewheel. I'm not sure if they make a 9 speed version of that, you would need a freehub body on the wheel.
This will explain the differences = http://www.sheldonbrown.com/free-k7.html

7 speed is likely to be cassette. But you can't put 9+ on a 7 speed wheel without modifications anyway. Most likely just need to swap the freehub and add 4mm of spacers to the axle.
See: http://www.sheldonbrown.com/speeds.html & http://www.sheldonbrown.com/k7.html
You'll need to spread the frame a few mm as well, but that's no big deal. I think derailleurs will be OK, but not sure.

I think you can also still get 7 speed integrated shift/brake levers for lower end shimano (Sora?). Then you wouldn't need to change anything in the drivetrain.

If the free hub is 8/9 speed compatible you will find a spacer behind the cassette when you take it off. 8 and 9 speed cassettes are the same size 9 speed uses a narrow chain to create the space for the extra gear. I have converted a Mountain bike from 7 to 8 but my free hub was compatible and all I had to do is change the shifters and cassette to 8 speeds. If I wanted to convert to 9 speed I would have had to change much of the group set to handle the narrow gauge chain.

The reason I wanted to change was to provide a granny gear and closer ratios in the middle gears. If you hunt around e-bay for the bits you will most likely need new rear wheel or hub, cassette, rear mech, front mech and chain and chainset leavers and cables for a 9 speed to work properly. An 8 speed conversion may be possible without too much work but I doubt a 1989 rear wheel will have a compatible hub. Might pay to stick to 7 speed and finding a cassette with ratios that suit your riding.

I appreciate the replies and have already accessed some of the resources mentioned. I'll give it a try and see what I can do. May be back for more advice