Hyundai Repair: 1997 Tiburon Transmission, paint expert, mitsubishi eclipse

Question
1997 Tiburon, automatic, four-cylinder, 160,000 or so miles.  Last mid-week the check engine light came on, which was not unusual, it has done this a handful of times over the years and always goes off after a day.  But it stayed on until Sunday morning.  I noticed it was off when I started the car.  Drove it about ten highway miles, then was going through some stop signs in a residential area when I felt the tranny acting strange.  To make a long story short, I have determined the car will now not go into reverse, or overdrive (and maybe not third, I am afraid to take it on a freeway to check).  When it tries to go into overdrive, the car will just drift down until I can get a lower gear to kick in.  If I shut the overdrive off, I can drive it just fine.  Fluid level looks fine both hot and cold.  Any chance this is a sensor of some sort, or is it time for the scrapyard?  The check engine light is now back on.  I think I can drive it far enough to get the codes checked, but I don't want the tranny go out completely halfway there.  I just went and bought a new Elantra (which seems to be a FANTASTIC car), but I hate to part with this car unless it needs a total tranny overhaul.  Thanks.

Answer
Sorry Gary,
I signed up on this website as an auto paint expert.  I do not know why i keep getting mechanic questions.  I feel for you, i have a 97 Tiburon 5 speed and drive it cross country with confidence except it was a little sluggish on top of Pike's Peak, Colorado and lost my brakes on the way down mountain when they overheated.  The car does seem like a toy car compared to my Mitsubishi Eclipse. I do not know if your car is a Throw-away car.  Probably only a certified or near certified hyundai mechanic could tell you and be prepared to pay for that answer.   Also i do not know what Aamco thinks of your car, did you call them?  They may be able to give you some insight over the phone.  I notice when i get the $99.00 transmission flush on my other automatic cars, it seems to help.  Did you ever do that?  A transmission will not work very good when fluids down deep with 160,000 mi buildup of sludge are interfering.  Did you smell the fluid on end of dipstick? did it smell burnt or dirty?  Dirty is cleanable, burnt usually means fried transmission.  But i am just an auto painter... i would call real transmission professionals before final decision of putting your old horse down.  What is car worth running good?  $1500.00- $1800.00?  Yes a transmission job could be anywhere from $700.00 to $2,000.00something or more.
Auto Painter