The short answer is to replace the seals if you want to spend the time and effort.
That said, there are now a lot of Teneres with a lot more miles than yours with original seals. I do believe in using a seal-mate to clean the seals now & then and think that cleaning any grit before it becomes a problem is one reason mine have lasted so long. (probably just jinxed myself)
Springs come down to your weight and how you ride, so even at the same weight what is right for me may not be what you would want. I'd strongly suggest NOT just buying springs generically, but call any of the good suspension names, discuss your particular situation and see what spring rate they recommend. You pay a lot for the labor of installation - the springs and seals are relatively inexpensive.