Dirty Engine/Trans means overhaul?

[pocketrocket]

Can anyone tell me how I could go about checking the engine/trans for my 71 SB 'vert? The engine was out of the car when I bought it but was told it was running when it came out with "49k" on the speedo. The only oil I see on the engine is below the oil filler neck so it may be alright but how do I know? The trans has some oil on it but not covered. Can the seals/gaskets be replaced? How can I tell if the trans is ok? ANYONE that can give a lending hand would be grealy appreciated! This 8 year project is just taking too long!