help!! I broke my car

I recently acquired a 1981 300sd. it was in storage for the past two years. it ran ok when i got it. but i decided to give it a little tune up. i did reasearch on this web site and decided to change the fuel filter. so last night i go get a fuel filter, unscrew the old one, put the new one in, crank the car and nothing. barely cranks over. so then i prime the fuel filter and now there is fuel in the filter. so i crank it again. nothing. barely turns over. so i think its the batter dying. i hook up my other car to it and the same thing. the engine barely turns over. please help!!!!