I'd start with knowing whether or not anything was done by the previous owner to the suspension to match his weight, springs / valving / oil viscosity. That will help to give you an idea of which direction you need to go. Also determine if your goal is to lose more weight. If you are at your target weight, then step one is to determine if the springs are in range.
Use preload adjusters to set static sag. 10MM rear, 20-22MM at the front. Then check loaded sag. If the springs are correct, you should be able to get 30ish at the rear and 35ish (maybe even 40 for the street) at the front. If you can't find a good balance of static and loaded sag with your current springs, you should change them. For example. If with 20MM static sag at the front, when you get on the bike, if the front only drops another 5 or 10MM, you will likely need softer springs. If with proper static sag set, you get another 30MM drop at the forks when you get on the bike, you need stiffer springs. Cranking the preload to either max setting may get you the loaded sag, or close, but not the static sag. It's important to have both, ie correct springs, to get the best from the suspension.
Setting sag is step one. If you can't get it set, and you are serious about getting the suspension correct, you can't really move forward until you have it correct. It is a critical step. That being said, next step is to determine if you're going to do your own work or have a shop do it.
If yourself, there is a dizzying amount of info on the web for this. A couple vendors, like Race Tech Suspension
can provide advice and all the parts and tools you need. There is even a bike / rider weight spring calculator on the site. Once the springs are correct, you will have to think about valving. If the previous owner had it changed to match stiffer than OEM springs, you may have to also have it changed if you go to softer springs. Maybe not, the compression and rebound adjusters are adjusters for a reason, BUT they shouldn't be maxed out in either direction to get the bike handling correctly. You have some ability to offset this with oil viscosity, but that's limited. You may be able to get low speed damping under control with oil, but it will also have an impact on high speed dampening, which really comes down to internal valving on the older bikes.
If going to a shop, they will guide you once determining you suspension goals.
Also, at this point it is almost a guarantee your bike's suspension NEEDS servicing anyway, so this is a good time to move forward with a proper set up, one way or the other. Few things will change a bike's character like properly set up suspension and serviced suspension.
The front is pretty serviceable at home if you are otherwise mechanically incline. The rear is harder, but also doable. If you have an Ohlins at the rear, all the better. I feel one of the reasons they are more expensive is the serviceability. They come apart easily and are clearly made to be service over many years. I rebuilt my rear Ohlins at home after downloading a service manual and calling Ohlins USA. They were helpful and I ordered all the parts over the phone. I didn't need to change the valving, so it was a simple refresh. Showa and Sachs do not seem as serviceable, and you are really better off having a shop take care of those. More important, don't forget the shock! Most seem ready to keep the forks serviced, meanwhile that poor shock goes on for years with nothing!