The speedometer, odometer, radio are out on my 95 Jeep Grand Cherokee?

We bought a used Jeep Grand Cherokee in pretty good shape. However, the radio quit pretty quick. The speedometer and odometer never worked. A mechanic friend looked at it and said he can't tell off the bat what's wrong, BUT that it doesn't have a cable. How do I get this fixed? Is it something I can do on my own with some car repair experience? (Can change a starter, battery, spark plugs, stuff like that.) If so, what part/s would I need and about how much would it run?