Hello Cat and welcome.
It’s great that you have your lumpectomy out the way. I also had a lumpectomy and 10 days of radiotherapy (5 whole breast, 5 to tumor bed).
Like you I was apprehensive, but for me it was totally fine. The sessions are over super quick and you get used to the place and the people very quickly. I didn’t really get much in the way of side effects, slight redness, but not really too tired or anything.
I was given Flamigel by the hospital, which I can vouch for. I was told to apply 3 times a day from the start. You just have to make sure you don’t apply it just before the session, as it needs to be absorbed into the skin.
Once I ran out of that I started using normal Aveeno moisturising lotion (green one) just after my shower (this was after therapy had finished).
I was equally very apprehensive about starting the hormone treatment, due to having heard such awful stories about side effects. I have now been on Tamoxifen for about a year and have luckily been absolutely fine.
It taught me that we are all so different and each person’s experience will be very different from the next. As much as you can, try to go with it and try not to worry too much about things that haven’t happened yet (Difficult I know, I’m a massive catastrophiser! 
).
I hope it all goes well for you.
Take care xx