Help with new car Options

[Stu37363]

I just bought a 1990 mercury grand marquis for my girlfriend.. when i first got it, it would die whenever put into gear. i beleive this engine is called a 302, its a 5.0 v8 that has been sitting for almost a year. anyways, i have installed a new battery, distributer cap, rotor/button, plugs, wires. drained old gas and put in 93 octane, raplaced oil and filter, and air filter. i still have a fuel filter, transmission filter, transmission fluid, and new antifreeze to put in. now for the problem, the car will accelerate fine at wot, and will rev fine in park or nuetral, but stumbles badly during partial acceleration in gear. the transmission fluid is much higher than it should be... could this cause the problem? is there something else i should be looking at? if anyone can help me narrow this problem down more i would appreciate it, as well as any possible causes and suggestions.