Welcome Tim. I've been into Marklin since 1990. I began with analog. Also a two rail d.c. 4X8 oval was my first layout. I bought a few Roco locomotives and still love those too. They make ac Marklin compatible ones also. You can run both digital and analog on separate tracks if course. Newer mfx, and DCC decoders are designed for the smp, or newer switched mode power supply. Conventional transformers can damage them, especially in a derailment or a short circuit.
The Marklin MS2, the CS3, and plus are multi protocol controllers for mfx, DCC, and the earlier Motorola format. They can operate Marklin,Trix, LGB, etc. The CS3s have a n integral powerful digital booster for a larger layout. The plus model includes a network cable jack for the S88 feedback modules used for automatic operations. This eliminates the need for a separate adapter and power supply for those.
By the way, I was born in Pittsburgh. I was just 6 when we moved here, but visited relatives twice annually through the 90s. We lived in Plum. My mother was from Midland. I still have cousins in Apollo, Brackenridge, Burrell, Plum, and one in Ambridge.
Since many dealers and shops are gone, most of us buy online from other states and even Germany. I have from AJC kids in Texas, Reynaulds in Illinois, Micro macro mundo in Miami Florida, Modellbahn Union shop in Kamen Germany, and Modellbahn shop Lippe in Detmold. Marklin has a US distribution center in Missouri. They have digital consultants Rick Sinclair and Curtis Jeng. Rick is also the Marklin employed repair specialist. They host periodic YouTube webinars which can all be viewed. There are several very good technical videos, but they are often in German. One who speaks good English is the model train fun guy. You will also learn a lot here from us members. You can also refer to the Marklin website for information about models, track, and accessories. There is so much to learn about making scenery and terrain as well. I must also mention a man Marklin of Sweden. He frequently posts on YouTube about many topics, in English. You can also find many in Instagram.

Edited by user 08 March 2024 20:18:37(UTC)  | Reason: Not specified

Many. With regard to the rolling stock attached to the locomotives (cars, vans, trucks - whatever you want to call them ), almost everything goes, but you might have to change the couplers and/or the wheelsets. Mostly, this is not a real problem and requires only a few minutes of easy work.

As to the locomotives, many other brands offer items already converted for use on Marklin's AC/three rail system, or then you can either attempt to perform the task yourself or have it done by a specialized dealer or repair specialist, etc.

Digital is a field of its own. While most people will probably say that it saved the hobby, one can meanwhile also have the impression that it has made everything vastly more complicated and no longer enables beginners to simply plug in a transformer and turn the knob on it.