I have a 2009 MacBook Pro 15". What would I need to buy in order to be able to use my LED HDTV with it, and which wireless keyboard works the best with it?
Macs made prior to 2010 only support video-out over the mini-Displayport, so it's a bit more complicated than just using a mDP to HDMI adapter, but it's doable. (You can see a complete list of which Macs support audio over mDP on Apple's support site).
You'll still need a mini-Displayport to HDMI adapter and an HDMI cable (or a direct mDP-HDMI cable if you can find one). In addition, you'll need to take the sound from your MBP's audio jack and route it to the TV. This is where it gets a bit complicated, as different TVs have different methods of doing this.
Most recent TVs have an input labelled something like "HDMI/DVI", with a corresponding audio input (something like "DVI audio in" or "PC audio in"). The audio should either be a 3.5mm minijack (like the output from your MBP), or a pair of red and white RCA jacks.
Once both the HDMI and audio connections are set up, switch to the appropriate input on your TV and check things out. If you don't hear any sound, you may need to check your TV's settings - some require you to manually change from sound over HDMI to sound via the extra input.
In any case, you'd be well served by checking your TV's manual for the specifics, as the ports and settings can vary from TV to TV. If you don't have it around, look on the back for the model number and Google it - almost all manufacturers have PDFs on their website.
As far as wireless keyboards go, why not Apple's own one?