I can shift into any gear but only first is engaged.

if mechanical connections , find and fix the loose part
if electronic selection check vacuum and shift actuator

When you "muscled it into neural" you broke the shifter. Most likely it will take a replacement shifter to repair.

Ok , so you got home , parked it and when you started it up the next day and shifted it into reverse... backed out... and went to shift into drive , it stayed in reverse ?
Have you checked to see that the cable has not disjoined itself from the shifter to the trans.?
Are you able to engage Park?

That is typically indicative of a fuel pump issue. It isn't necessarily the fuel pump itself, but the way it is positioned in the tank when low on fuel can keep it from getting fuel.
If you fill the tank and find however that the problem still exists then the other cause is related to parking.
Your Buick has a safety mechanism that will not allow it to be started if not fully parked, called the Brake Transmission Shift Interlock. Not only does this solenoid controlled component not allow you to shift out of park without applying the brake, you also will not be able to start it if this mechanism is faulty, or something in the gear select linkage prevents the shift selector from properly engaging the parked position. When on a hill and you shift into park, the vehicle weight is rolled against a component of this system, preventing it from properly "registering" the parked gear select position.
What you can do the next time you need to park on a hill is with your brake applied and the gear select in Drive, apply the emergency brake and hold it down, THEN shift into park. Then release your feet from the brakes. This should help.

If you drove the vehicle to the driveway, and then the next day got in it and started it, tried to shift, went nowhere, shifted back into park and shut off the engine, I would have to say no damage done, but I will bet that the dealer will try to sell you another whole new transmission anyway. I bet the bad seal just needs to be replaced and then fill it with fluid and all will be well. If they try to sell you a new one, tell them you will call them back, call an independent transmission shop, and ask what they think about the situation and go from there.

Sounds to me like there is too much weight on the "park" gear. Have someone push the car forward a little bit, and do it gently, to release some of the pressure on the transmission, and it should shift from Park without a problem. I highly recommend if parking on an inclined driveway, or any hill, to use the parking brake if it is possible to do so. Good Luck

it sounds like the problem started with the brake shift iterlock switch by forcing it he now broke the trans shift cable mech at the column

check the clutch slave cylinder fluid level.if its low it could be leaking,may need checked and replaced. clutch also could be bad.

Sounds like the PNP switch or the Park/Neutral switch is out of line (adjustment). There is very much information about this on the internet.

Just today I was called by my garage because the mechanic could not start the car. I had my 1993 960 in for freon (134). Over the phone he said the starter would engage but no start. He was about to recommend a new fuel pump because no fuel was reaching the engine. So I said wait. I went down and while he was not looking I did the shifting routine of: brake depressed, key on, move shifter from Park through all the gears several time, then key off. After this I could start the engine and drive off. On the transmission is a PNP inhibitor switch and a Park/ Neutral sensor switch that cause no start and no shift situations. Oh yes, I did not bother to tell him what I did! He spent six hours trouble-shooting and would have charged me.

My next project is to wire around these trouble makers. I always drive in "E" and I do not care if it will start in all positions.

William White