Welcome aboard!
As far as you having trouble shifting from 1st to 2nd, it sounds like you might have some sticking or leaking valves in the valve body. On the same note, there is also an updated Turbine Speed Sensor (TSS) that has helped plenty of folks with some similar issues.
As for the O/D light... I take it that you mean - while driving around and turning the O/D on and off, after about the tenth time, the light begins to flash. If not, well I've never sat there and pressed my O/D button on and off ten times while sitting still. In any case, you might need to take it to autozone and see if they can pull any codes from it. If they can't, then that will mean that you will need to take it to a tranny shop and have them put it on a true scanner and test drive it. They can get electrical readings and find out whats wrong.
Absolute worse case senerio, that is if you don't have the money to get it fixed right now - while at Autozone, grab yourself some Lucas Transmission Fix. If you have leaking valve's, this stuff can help with that. It will not fix your problem, but only get you by until you can get it fixed properly.
