You can refill the fronts if you can get to the valve nut. I can on many racecars. A 7/8" socket will remove the valve. You'll want to pull the "guts" out as well. Do this by grabbing hold of the stem you'll see and wiping the side of the hole as you lift. You should bring up the stem bit that has a spring as part of it, plus a larger loose spring, and probably a washer or 2 of the same large diameter. Now, pour in some oil. Hydraulic oil, or engine oil, no more than 20W. Bounce the car fender slowly and keep the hole overfilled until there's no air bubbles. Make a mess. Now re-install the valve assembly. The shim washer goes uppermost between the spring and the valve seat. Tighten the nut. Now, the reason the shock was low on oil was it leaked. It WILL leak again. There IS a fix for that, but requires replacing the shock, which you might consider doing regardless. I know a guy what sells 'em. Peter C.