What's involved in changing the valve guide seals on a stock 5.0? Is it something the average "Joe" can do in his garage on the weekend?

 

you can do it in your garage but you need a special spring compressor and theres a tool that used an air compressor to pressurize the cylinder to hold the valves closed. unless you plan on pulling the heads

 

Here's a quick description
http://www.ehow.com/how_2110646_repl...ls-engine.html

Here's a more detailed description.
http://www.newenglandclassics.org/Ar...eplacement.pdf

They are not mustang specific, but you'll get the gist.

 

changing seals is easy with heads off the motor, just need a spring compressor for valve springs and then tap the retainers and it should unseat the lock holders

 

You can do it with the heads on the car but you have to be careful on not dropping the valves into the cylinder. Bring a cyl to TDC, take the rockers/springs off,change the seals and reinstall. Then bring the next one up and do the same. I was tired of waiting on the seals for my GT40s before I installed them so I rapped tape around the valve stem to keep them from falling in and installed the head then when I got the seals I did this. Some valves started to slide in but stopped at the piston and still had enough stem left to grab and pull back up but don't do this thinking they won't fall. You can get a spring compresser from the part store for cheap.