As much as it pains me to say it, you need not dump $500 into your Hard Rock all at once. There probably isn't anything fundamentally wrong with it that steady incremental replacement with quality components wouldn't address at an as needed basis.

You will need basically everything eventually. Why not get your monies worth and learn some new skills while you are at it? The $500 you mention is probably to have a shop do the work. Just about every task on a bike can be done at home with very few tools and any special tools needed tend to be fairly in expensive.

You can re-cable a bike with housing for under $30-40. Brake pads will set you back -$25. A bottom bracket is ~$25 & the tool to do the job is around $12. Axle sets with cones and balls are ~$20 or so. The cone wrenches and axle vice to make the job easy are about the same...Boom! A new bike!

If it were me & I simply had to invent a reason to spend money on a commuter, it's be on a tubeless capable wheel set. Pull out the nail, shove in a DynaPlug if it didn't seal automatically and carry on as if nothing happened. I'd tell myself that all the times I avoided being late to work pencils out.

If you can make pancakes or bake bread, you can build a wheel. It is little more than following instructions. Once you have it laced, take it to a shop for a tune & true if you are unsure if your abilities.

Bike shops entire service model is to do what customers believe they can't or have no interest in learning. Customers are willing to pay dearly to remain ignorant. Learn a thing or two and there is simply no reason to justify a $500 spend on a Hard Rock...or any bike service for that matter.