Hi Darcruze,
Firstly, welcome aboard, you will find heaps of great info/advice here.
Secondly, repost your query in the 'TJ/YJ/Brute Wrangler Drivers' section and you should get a better response.
I'm nowhere near as knowledgeable as some of the people on here but for what it's worth, if the rest of your gauges are working, the speedo problem probably relates to the connection at the transfer case. It is located under the Jeep on the LHS, forward of belly skid skid plate. Sorry I don't have a pic handy but a quick search should reveal what you are looking for.
As for the revs, I'll have a guess and suggest the Throttle Position Sensor (TPS) needs replacing but like I said, there's others on here who actually KNOW what they are talking about.
Good luck, we have to keep the mighty 97's running!