OD stuck off, tachometer is 3-4, guzzling gas, is my transmission going?

So basically your tranny is not shifting? Could be stuck shift solenoids. Check the tranny fluid, you may just need a fluid flush and filter change. Could also be clutch pack or torque converter. Solenoids are around $30-40, sometimes it's cheaper to just DIY replace them than to take it to a tranny shop which more often than not try to sell you a bill of goods you don't need.