32 year old guy wants a first tattoo but hesitant to get it.  ?

Two best options IMO. 

A) Her portrait...spend the time to find an exceptional portrait tattoo artist. 

B) An image of something she liked or did. For example my one Grandmother made a variety of crafts. She was also a dedicated member of her Church Choir and collected bells. For her I'd get a tattoo of her favorite craft project...a mug rug with the initial of our last name. 

If you're not sure there are lots of other ways to honor your grandmother that don't involve permanent ink. A photo album, save a shelter animal, plant a tree or donate to her favorite cause. All meaningful and helpful.

I got my first at 43 years old.  Tattoos are who you are.  Leave grandma out of it.  What are you thinking of a RIP tat with your grandma's name.  NOPE  no good.  

first rule of tat's.....if you don't know what to get..........then you don't get one. 

Because you'll regret it soon enough. 

When you are 100% SURE of what you want.......then get one. 

You lived a good life of 32 years so far, why change a good thing? In memory of your grandmother wouldn’t it  be more important, that you stay the way you are, the way she remembered you?

If you're hesitant, pay attention to your feelings and don't do it. I doubt your dead grandmother would feel honored in any case. 

Visit a few tattoo shops in your area and ask then any questions you have, you may even see some one getting tattooed so you know more about what to expect. They can even draw up a tattoo that you will want to get tattooed. If you're not sure that you want it, you may end up regretting getting it. If you love it, you won't regret it. 

My grandmother died in 1965 . . . . and I can still remember her quite well without the aid of trashy body adornment.

Google tattoo studios near you, look at the artists and their artwork and decide which artists style you like the most. From there schedule an appointment with your preferred artist and tell them what you want, They are friendly people and will help guide you to a possible design.

 Depending on the complexity and size it could take anywhere from 1 to 5 hours to fully complete. My half sleeve took approx 20 hours with multiple appointments to finish.  Usually first the lines are done with a single needle, once the lines are done then shading comes next with a fork like needle, the shading is the more painful part as it requires going over the same spot a few times for the proper application of the ink.

The outer bicep is a pretty easy spot to get a tattoo as far as pain, once you get around the armpit or elbow is where its starts to hurt. But its all tolerable pain, best way to describe it is someone scratching a bad sunburn with a toothpick. Make sure you have some spare cash because tattoos ain't cheap if you have a quality artist and be sure to leave them a good tip! Good luck!