2010 Sonata shift lever difficult to move, not always reaching far enough to hit "D"

My Sonata developed a problem with the shifting mechanism. The shift lever became slightly harder to move. When this happened and how quickly I can’t remember, but I know it’s been a nagging problem for about a couple of years.
About a year ago, when I put it in Drive, the “D” indicator doesn’t always show up and stayed blank. However, it was in Drive because I could drive it. The engine light would then come on, perhaps because it detects that something is not aligned right or something.
If I then from then on, every time I put it in drive, I push it a little harder until the “D” shows up in the display on the dashboard, then after about 24 hours or so, the engine light would come off again.
So that kept going for about a year.
But then I ran into part 2 of this problem. I couldn’t get it into the drive. It would stay in neutral even though the level was in the d position. Before I got away with it, but now I don’t. I then put it into the manual up/down gear shifting mode. No effect. The level goes there, but accomplishes nothing. End then, I couldn’t move the lever back to the left side, into drive! I ended up stranded in a parking lot!
I tried doing the shift-lock-release button thing, that’s hidden underneath that little cover, but that didn’t work.
I ended up taking the cover off (the big plate with the P R N D indications), and discovered how there is a cable that’s pushed by this white box that has the lever mechanisms in it. Something is out of whack somewhere, in addition to possibly the cable moving stiff.
I’m guessing that some WD40 in the cable on both ends might help make it move better. I’m hoping that the linkage, the part that goes into the transmission, that that isn’t the culprit.
I tried to take that box, the lever mechanisms. Took off all screws in sight, but it won’t budge. How do I remove that whole lever mechanism box, so that I can see and inspect and see what’s possibly wrong there?

What does it take to get you to go to a mechanic?

I’m afraid that a mechanic is going to round up actual time worked, replacing parts that didn’t really need replacing (eg. recent parking cable replacement - I’m just not buying the fact that the cable actually had to be replaced - I think it could have been done up with some grease lubricant or something get things moving - but no - $600 just like that).
I’m afraid that a mechanic will arbitrarily replace the shifter mechanism box, cable.
Before I risk all that, I want to try to fix this myself.

I understand, my comment was generated by the fact that you have been dealing with this problem for two years without doing anything. I wish I had some helpful knowledge here but I don’t so I will just wish you well and hope someone else can help.

Call your local dealer and ask if Technical Service Bulletin 09-AT-013 applies to your vehicle.

This TSB addresses a problem with the transmission range switch which can cause it to be difficult to shift, and cause the Check Engine light to come on because the computer is confused as to what gear the transmission is in.

Tester