The diy portion would include shaft / rocker removal but not much else. You would be able to install the bushings but it is better for the shop to do the job complete as they will have / can make a bushing driver.

Getting new parts prices is a good jumping off point. If new bushings are huge $, there has to be something off the shelf that would work. If the shaft is worn and $, getting it centerless ground then honing bushings to fit is an option. Just make sure the bushings are undersized enough. If lateral play is too much, generic precision shims can be had to take up the clearance

This car has overhead cam where one end of the rocker rides on the cam and the other on the valve tip correct? If so, these designs are relatively immune to swapping parts ( at least for modern engines anyway. ) But it is good practice to keep worn parts together where possible.

If this is a pushrod engine, parts can be swapped without much issue.

Given you drive 1 K per year ( and I'm guessing not much at freeway speeds ) parts that are on the worn side will continue to go for years so don't be too worried.