Hey Mo,
It is entirely possible to do for less than 1000. Your biggest headache is going to be the headliner. It is a $29 dollar part that makes you take the windows out to do it "correctly". I recently did the interior in my fiance's 66 and just left the headliner for now since I will be removing the windows for paint. We just wanted a nice driver interior because a full resto is coming up after we get married. We bought carpet, door panels, front seat covers, arm rests and pads, laquer paint for the doors, a woodgrain instrument cluster, an aplique for the glovebox, a set of kick panels with speaker holes, a black hump hugger console,and a plastic dash cover for about 550.00 from Mustangs Unlimited. You can do the seats yourself, just take your time and purchase a good set of hog ring pliers. Taking your covers off in one piece instead of just cutting them off helps alot. Then, you know how they come off so you know how they should go back on. Her car didn't get new seat buns right now because we are going to convert to pony seats. The door panels were a simple remove and re-install just make sure to pull the tabs out of the clip holes and not push them into the door panels (found out the hard way!). The dash cover was a cheap way to cover a small crack in the original dashpad. For all but the most die hard purists, it is actually a good looking piece. Fits nicely, really finishes the driver restoration. The little things make a huge difference also. If your window crank handles or door handles are too bad to be polished, invest in new ones. This was my first time working on a older model and it was a blast! Give yourself plenty of time though. Do not think that it is a weekend job. All told, it took me a month with life getting in the way here and there. It is very rewarding though because you watch it come together and know that you did it yourself.