As far as the old layout goes, If it is troublesome ,I would scrap it if it were me. I am going to paste a little note I like to send to beginners if I may
Welcome to the hobby that can be as big or small, High tech or low tech as you want it to be. . The track with plastic ballast attached to it is not interchangeable between manufacturers. Wait I should say I understand it to be that way. I don't use it myself. All other HO track is interchangeable. I have been in this hobby for 50 years + -. But I have been a serious modeler for last 15 years, my sons grew up and left. Then they came back later. In my opinion get a 4x8 sheet of plywood first, build a small simple layout not too much on scenery but do some to learn from it. run it for a while. After about 6 months of running tear it apart and start over making the changes and improvements you have discovered. run it for a while, and do it again. By doing this you will learn what you like and don't like inexpensively and without wasting a lot of what no one has enough of, time. This way when you decide to build a layout you will have some experience and already made many of the mistakes beginners make knowing you are not keeping it.
back to track. I use all flextrack with a few, very few exceptions. I use code 100 but if I were starting over I would use code 83. also get Peco switches / turnouts. I am slowly replacing all of mine with Peco. Much better quality, little more money but well worth it.Enough for now feel free to PM me any time. Oh yeah find someone who is in the hobby and ask questions and ask for help.I think you will find that most MRRers are good guys.
When using flex track off set or stagger the joints. I like at least 12 inches between them. this will make you connections smooth and usualy trouble free, there are always exceptions. when you do this you will need to either cut the spikes and cleats off of the ties at the jointor or remove a couple of ties. I would suggest soldering the joints only after you are sure that it is your final layout as it is not much fun to unsolder it.
I hope this helps you some. Flextrack takes patience. All of track laying takes time and thought to do it correctly.
Les