mahadown

hi everyone. new to forum. first post. i was just given this van because the owner wanted it off of their farm where it was sitting for 4 years. although i don't have a huge knowledge of car mechanics i have always loved old rides (i'm an alaskan fisherman). i just couldn't stand the thought of this van going to a junk yard. so i just started working on it. it has LOTS of work to be done. i got it running. the engine sounds good. i don't want to drive it before i do some major work tho'. but i did take it down a side street because i couldn't resist. my question is broad but maybe someone can set me on the right path. it seems to have no power when it goes. i got it up to about 15-20 mph and thats about it. i know this is a ridiculously general question but where should i start as far as working on this problem. could it be the tranny, linkage etc. was just wondering if there was some "best bet" starting point that i could go with down the list to address this. any help for a first time dodge owner/non mechanic would be great.
thanks and looking forward to exploring the forum.