This is impossible to answer given what you have told us. We need to know more like:
What was the pathology?
What were your tumor marker levels before surgery? What are they now?
What, exactly, did the CT scan show? If there were enlarged nodes, how many and how large?
What, exactly, did they find in your lungs. If you dont have copies of the CT scan reports, you really ought to call the doctor and ask for copies.
It would also help to know your age and marital status and if you are interested in having kids in the next few years and stuff like that.
That said, if you were to tell me nothing more than the little you have posted so far, I would say chemo. Radiation is going out of style for this cancer, and chemo is a systemic treatment that would also treat anything in your lungs - if there happened to be anything there. Also, chemo would work on seminoma and nonseminoma, so it doesnt matter if they have the pathology slightly wrong. Nevertheless, I wouldn't blindly go with chemo as it is entirely possible that there are other options, especially if there is only one node and it is small.