Greetings and welcome.
I too came back to digital recording after a period of only about 5 years or so. I had been on Cakewalk pro 8 and due to OS upgrades and drivers unavailable for the sound card, I got out of recording. When I returned, the OS was Vista and XP was new.... and the DAW available was Music Creator 4. I had read enough on the forums to know I needed an external interface to handle the sound input & output. So yes, buying a decent interface IS THE WAY TO GO.
Even with the right gear, it took me almost 2 frustrating weeks before I got sound out of the speakers. There is a learning curve and don't let your computer programming education fool you into thinking it should be easy because of that..... we're on this side of that fence. You must join us here and learn this as we did. Come to the dark side..... The learning curve applies to everyone.... how quickly you get up the curve depends on you. We're here to help answer questions when you run into road blocks. No doubt, we've been there before and can assist.
Once you get the inputs and outputs figured out it becomes simpler. Once you get the interface setup, it should not change, again, making things simple. You will always need to select the desired input and output to a given track and buss.....
For now, think of a buss as a track that can accept the input of several tracks. Such as several guitars or several vocal tracks with all of them needing the same FX treatment. You can have as many busses as you want. I use them and often have 4 to 6 busses depending on the project at hand. Envision a pyramid..... tracks at the bottom, busses on top of that and the master buss at the top. Signal flow is up.
Divide the musical world into 2 segments.... audio is one..... midi is the other.
Audio is simple..... sound from a mic or audio input goes to the interface, the signal is routed by software to a track. You choose the input for that track from a list of ALL the audio inputs the software can "see" in the computer. Output from the track is defaulted to the master output buss and from there to the interface and the speakers.
Midi is similar.... but there is no audio in the initial stages. You set up midi tracks and select the input from the available midi input sources, and that data gets recorded into a midi track. There is an associated or linked audio track with that midi track. The audio track will contain the inputs and outputs of a software synth which you have selected previously. The midi date goes to the synth and the synth plays the audio. the rest of the process is described ion the audio paragraph.
Midi can also be assigned to channels. Many synths ( cake walk sound center is one) are one channel synths. TTS, mentioned in posts above are multi-channel synths and you can assign up to 16 different instruments to that ONE INSTANCE of the synth in your project.
Some time back, I created this page to assist other folks who were getting started:
http://www.herbhartley.com/hh2_edited_slimmer_005.htm Read through it carefully. If you have questions come back and ask specifically about an issue. Look down the page to ADVANCED TTS and work through it.
Hope this wasn't too insultingly basic..... but do ask questions if you get stuck or just want to know.
MC6, while called the "beginner" level DAW by cake, is anything but "beginner" in what it can do. I used MC4 as my DAW for many years and it did a fine job. I have since upgraded to X1essentials, which is now pretty old as well..... but have a listen to some of the music on my website music page which I created with these "basic level" DAW's.