Any Tips on TIU Replacement?

I believe it depends on whether the new TIU has the same id# as the old TIU. If it does, then it should be a straightforward replacement and the remote should work with the new TIU. 

If the new TIU does not have the same id# (counting the red light number of blinks as compared to the old TIU number of blinks), then you will have to:

1. Use the remote (edit TIU address) to change the old TIU to the same id# as the new TIU.

2. Turn off the old TIU and turn on the new TIU.

3. Now, using the remote (edit TIU address), change the new TIU to the same id# as the old TIU had and you should be all set.

If you are using the magic bulb trick to improve DCS signal with your old TIU, you will need to remove those magic bulbs. As having them will kill the signal with a Rev L TIU. 

I would also suggest backing up your remote to a computer using the old TIU, just in case. I only own 16 locomotives (7 TMCC, 9 DCS) but have my remote backed up so I don't have to reenter everything if I ever reset the remote. 

Lou1985 is absolutely correct.

The Version of DCS should also be the same on the remote and TIU. When you first turn on the remote it displays the Version the remote has loaded in it.

For the TIU Version:  Menu/ TIU Setup/ TIU Version

You only need to reset the remote and TIU if you have an early Version like 2.X

I recommend loading the latest Version in the pair if not already there. 6.10