I have three of the HF trailers. 2 light weight and 1 "heavy" weight (1800 lb - 40597.)
First, go to HF web sight and download the manual for the 40597 which gives you a schematic with part #'s so that if you ever had to make repairs the schematic would be helpful (you said you didn't know much about this kind of thing).
The light weight trailers have 1" bearings and races. These come in sets (bearing/races), are quite common and can be purchased in any auto parts store. The sales person usually doesn't even look up a part no. - Just goes back and picks them up. Always replace both bearing and race.
I carry a couple sets in the tool box always.
HF part # are Bearing #76 and there is no part # for the race- probably comes as a set. The races are pressed into the hub and have to be drifted out with a punch or screwdriver (an old screwdriver). This repair is "do-able" on the side of the road if necessary(but you'll need wheel bearing grease). You can also purchase the complete hub assembly from Northern tools or from Tractor Supply as well as other dealers and most auto parts stores. This makes it much easier in an emergency situation.
Re-pack your bearings ever year and you should not have any trouble. An inspection when packing will let you know when the bearings need replacing. (They're inexpensive enought till I just replace them when repacking)
NOW here's what I don't know - Someone help be out. -- the Heavy weight trailer may have a 1 1/4 inch bearing and race (my A-liner does). I've not had this one apart so I don't know. NOPE, just checked. Mine's got 1" bearings.
I hope this is what you were asking for.
HTH's
Geron
If it's not broken, you're not trying hard enough.