"Fix up" is relative. If you want to modernize it, you'll spend more than if you just want to make it roadworthy. Without seeing the bike in person and without knowing the fee schedules and markups at bike shops (LBS) in your area, it's hard to say just how much it will cost. Here are my thoughts, given the age of the bike.
First, the wheels. Are they free of heavy rusting (light surface rust isn't an issue)? Are the rims free of cracks (look around the eyelets--where the spokes pass through the rim itself)? Do the braking surfaces appear heavily worn? If they're in good shape other than the rear rim being tweaked, you can still ride them. The wheel (maybe front and rear) will need truing. The hubs will probably need an overhaul, which usually is nothing more than cleaning the bearing races/cones, possible installing new bearings, greasing, and adjusting. This work could be $50, more if replacement parts are needed.
Tires: Replace them. If the wheels are original, the wheels are 27", which is not quite the same as the 700c used on modern roadbikes. There aren't many tires made today for 27" wheelsets. Fortunately, Panaracer makes their popular Pasela tires to fit 27" wheels. They're quite good and very reasonably priced. Continental also offers its Ultra Sport in a 27" version. You can often find either of these tires for about $15 each. Also might also plan on replacing the innertubes and rim tape, which will add about another $15.
Drivetrain: If the chain isn't rusted or worn, it'll be okay with a cleaning and lubing. The freewheel (cogs on rear wheel) is also subject to rust and wear, but less so than chains. Should the chain and freewheel need replacement, it still won't be expensive compared to what it would cost on modern bikes. Freewheels can be had for less than $20, and chains even less. Labor isn't much of an issue here.
Cables: Unless these are in good condition, replacing your brake and shifter cables/housings is not only a good idea for safety reasons, but doing so will help ensure you get the best performance/response from your brake calipers/levers and derailleurs/shifters. Cables and housings aren't expensive, but it does take some time.
Brakes: Pads (or "shoes" or "blocks") can be inexpensively replaced. This is a good idea if the current pads appear worn, are embedded with road debris or metal, or have dried out over time. If you felt the bike warranted spending a few more dollars, you could replace the old calipers with a a better performing modern caliper. And if the brake levers are in poor condition or are uncomfortable, you can replace these, too. Many new lever sets come with cables & housings included.
Other stufff: The headset and bottom bracket may need to be overhauled. This is similar to the work suggested for the wheel hubs. Mostly labor. The derailleurs could probably use a thorough cleaning and lubing. Hopefully the seatpost can be easily removed from the frame. It will need fresh grease applied to it. Same is true for the stem. You might want to replace the handlebar tape, depending on condition and comfort.
Saddle (seat) and pedals: This depends on your personal choice. Your LBS can help you select from the many options.
So, you can see that the $ might add up here. If you need a bike, and this one is in good condition and fits you properly, then you can invest the money in it and enjoy it. This would be an ideal project for the home bike mechanic. If you don't understand bicycles, then you want to leave it to an experienced wrench at your LBS to do the work. And don't bother shopping online for these parts, other than perhaps a set of tires/tubes. You won't know what you're buying (no offense) and will end up buying the wrong parts. Bad idea and bad suggestion. Just take it to a reputable LBS and have them write up a work order. You can then decide if it's a reasonable amount or if it's too much. IMO, that's the smart way to go. You only have $10 invested so far. Good luck.