The valve cover is easy and you can do it yourself. If its the rear main or maybe the pan arch then there are a few guys I can give you recommendation but both are a bit of work.
If you end up doing your own wrenching, don't forget your 20% off parts discount for being a card carrying TLCA member at Toyota Carlsbad. In addition, they offer a 20/20 deal - 20% off parts for any vehicles 20 years old and older.
Not uncommon. Just tighten them until they are barely snug. I know that's a super specific torque amount, but you do not want to over do it. Read this thread about the VC toque specs. If that doesn't solve your leak then the valve cover gasket is easy enough to replace as a next step.
I did the valve cover gasket on my '95 80 about a year ago. Not a hard job, but time consuming. The valve cover bolts closest to the firewall (where a leak mimicking a rear main seal problem might occur) were literally finger tight only. The original gasket was brittle and cracked, so while tightening the bolts might have helped, that alone was not likely to fix the problem. After the gasket replacement I still have an occasional oil drip but 90% of the problem was resolved. Before doing the work, I did a engine compartment clean up at one of the car wash bays around town that allows such things... not many do these days. One of the hardest parts of the job was changing the spark plug seals on the valve cover. Make sure to get the gasket kit that includes these seals. Getting the original seals out was a real pain in the neck and brute force process; I'm sure there's a proper tool for that job, but a hammer and chisel works... When reinstalling the bolts I used a little Loctite red thread-lock compound on them to hopefully keep them from backing out again in the future. Pretty hard getting a torque wrench on the rear bolts as well, I recall using a 1/4" drive with two universal joints to reach back there.