what gearbox oil level and only getting reverse gear?

If you had no Reverse before oil change then you have a broken band. Holding gear lever slightly out of drive will make it go into limp mode and move in third gear only. If it only happened after oil change then I suspect that you took out the selector pivot bolt for the manual valve to refill. If so then the manual valve is disconnected. The filler plug is under the inner selector cable. For specialist www,fedauto.co.uk

mags
October 2010

when you fill an automatic gearbox, you must put in the correct type/amount of fluid, then start the car, and keeping the brakes ON, go though all the gears to settle the fluid thoughout the g/box, this should solve your problem, if not you might need to go to auto transmission techie, (not main dealer), but auto boxes are expensive to repair, might be cheaper to get replacement from good scrappy. Good Luck.

hope it helps
October 2010