Sleeves are a dime each at The Attic. It's actually cheaper than most on line outlets.
This is how I buy used records...
Look at the record for any obvious defect that won't clean away. Once you have a pile that pass that test, find a dark corner and inspect them with an LED flashlight. I use the 9 bulb cheapies from Harbor Freight. These really make fine scuffs and scratches jump right out. Then of course you have to be able to discern a scuff from a scratch. Scuffs will look "hazy" under the light and don't generally have an audible effect. Scratches will be much sharper in appearance and no amount of cleaning will get rid of them.
Many opinions on cleaning fluids. If I were in your position, not having kids and being unsure of my steadiness of hand, I would just buy one of those Spin Clean things and be done with it. People really obsess over what fluid, but IMHO any fluid or even just water will be beneficial for most of what you will find at HPB.
Then there is the issue of deadwax markings. I'll hold it to my one rule of thumb for ease. Handwritten almost always trumps stamped, and the more writing, the better.
Oh, and check the label for spindle marks. Light ones are okay, but deep ones are a good indicator that the record was owned by someone who didn't care for it.
At HPB, don't let price sway you into thinking it is an indicator of condition. They seem to make most of their pricing decisions based on stock on hand. I've seen minty records in the buck bin and garbage in the locked box.
What time are you going? Perhaps I could meet you.