Okay, the first question is "how handy are you?"
The hubs and brakes on a pup aren't particularly complex, and if you are comfortable with mechanical work, then the work is pretty easy to DIY. However, based on your story, I suspect you aren't too comfortable with this. If you think you are capable, lots of good YouTube videos go over the process.
When was the last time you had the bearings repacked? Manufacturers recommend this maintenance annually, although I usually do mine EOY because we don't travel a lot. If you have not been servicing the bearings regularly, they could have dried out and seized, and that is my guess of cause.
The other option is as @JFlightRisk points out. Either way the hubs and brakes will need full disassembly and rebuilding, especially as the lube you sprayed in hasn't helped either system. You may need brake parts, bearings, seals, and possibly even spindles. Parts are pretty easy to obtain and not too expensive.
If the thought of doing that yourself made you cringe, find a reputable local mechanic or dealer who will do the work for you. No specialized skills are required, so many mechanical shops can do it. The trailer is over 20 years old, so it doesn't need to be an RV shop (no warranty concerns).
And welcome to JOF. With a '97 pup, what took you so long to find us?