Welcome to Subsim.
Greatings from Reno Nevada USA.
The very first thing you need to do is make sure of what version of the game you are running, the original Silent Hunter or SH4 with U boat addition.
If it's the standard SH4 you need to install the 1.4 patch from UBI.
This is the last patch for that game and is a MUST in order to play. It fixes a lot of "bugs" found in the original game.
If you have the U boat add on you are patched to 1.5 and that is all you really need to play.
As to your questions the answers will depend on which patch you are running.
There is a way to add the degree wheel to the map but you need to edit a file and which one depends on the patch 1.4 or 1.5. All the bigger Mods have this added. TMO, RFB and FOTRS
There is also a way to input range into the TDC but it depends also on the patch.
It is always a good idea to give you version of the game when asking a question, there are so many different patches and mods out there the answers will be different for each.
Magic