Yes I can shift from 1st to 2nd while driving under 30 MPH
You say 1st to 2nd, but can you downshift from 2nd to 1st while underway without any grinding? Grinding would, I think, be conclusive for a bad synchro. No grinding...I'd want to check every other possibility (even knowing that the experts here are indeed experts).
The workshop manual lists four possible sources and actions:
1. Loose powertrain/drivetrain mounting bolts. Tighten bolts.
2. Pilot bearing. Install a new bearing.
3. Internal component damage or wear. Install a new transmission.
4. Gear teeth worn or damaged. Install a new transmission.
Considering the magnitude of 3 and 4, I'd want to be very sure about 1 and 2.
If it was my car and I wasn't going to sell it, I would take an action that is not in the workshop manual: Don't decelerate in 1st gear! Meanwhile, be on the lookout for a used trans to have in case your trans goes further south. Hard to imagine a spare trans is ever going to lose value.