1. I would personally not bother with the hinge fix unless and until you start using the machine more intensively than most people tend to do. If the machine is going to sit around on a desk most of the time, just leave it open, and most machines in any case will go on indefinitely with the stock hinge. If you read around about it, the fix becomes necessary when the machine is opened and shut a lot, so that the spring gets deformed. If yours came new in the box, you do not have that problem. You can, furthermore, buy replacement ribbons these days from an online seller should you get into trouble further down the line.
2. The memory card makes a big difference if you are intending seriously to use the machine, say for writing or taking notes in class (for which it is ideally suited - check out the way that you can insert a drawing of, say, a graph into a text document, even in Works). I have a post reporting my findings in the Newton section of these fora. The expansion cards, however, can be expensive. The best way to find one is in an eBay Newton: ask for a photo of the bottom, and if two cards are under the cover, you have the expansion card. Most sellers don't know the difference. That way, you will have a parts machine too, and the total cost will likely be the same as what one of the memory cards alone would typically cost.
For tinkering purposes, however, the machine will work fine and for a long time just as it came to you.