You've run into the one of the biggest challenges in composing: how to communicate your musical vision to your performers. Composers have spent the last 1000 years or so figuring out how to communicate with performers, and at this point music notation can communicate a lot of information with just a few symbols. Scoring is more of an art than a science at this point, so you're going to need to put in a LOT of work if you want to catch up.
First off: Go buy Finale or Sibelius. If you ever think you're going to have access to live musicians (or want to), you need to make that investment. I use Sibelius, it's simple to learn and powerful once you want to start fiddling around.
Sibelius can handle making all the parts you're talking about (as long as you tell it to print transposed parts for the instruments that need it), and its default spacing/alignment choices are usually pretty good. It also highlights any notes that might be outside an instrument's register in red, although it's usually a bit conservative so you'll need to actually research instrument ranges to be sure. Just remember to make backup copies of your working file every hour (or half-hour, or less), and before starting any major revisions.
If you're really committed to doing this, here's what your timeline looks like:
Day 1: buy Sibelius or finale. In fact, go back in time and do this yesterday. Mess around with it and figure out how to put in notes of various lengths. Sibelius is a bit rough at first if you don't know the hotkeys (i.e. "i" to choose which instruments are in the score, "n" to change from note-selection to note-input), so look for youtube tutorials and ask here if you have specific questions.
Days 2-6: Create a score for your orchestral piece, and keep getting used to your scoring program by inputting notes for each part into it. Personally I think it would be better if you put each part's notes in by hand, since nothing will teach you how to read music faster than seeing your own ideas represented by notes. Play back the parts individually as you're inputting them a lot to make sure you've got the notes and timing right. If note input is just too slow and you can figure out how to get it to work I suppose you could try to do a midi import. Imports are always dodgy though, so you'll need to sanity check them: if a bar looks really complicated and you KNOW that nothing too exciting is happening at that time, then something's gone wrong.
By day 7 you should have ALL the notes input into your score. You should be able to hit play on your scoring program and have it sound vaguely right.
Day 7: Plan out dynamics and texture. Start at the most general level: "Bar 1 is not too loud. Get louder in bar 7 and bar 8-14 is quite loud...." etc. Then plan out each part specifically: "violins start playing really connected notes, but at bar 15 they play short and sharp, and then at bar 23 they're back to sustained" etc. Even if you don't know how to communicate what you want yet, you have to know what you want. You should have a list (or multiple lists) of what symbols/commands you need to know.
Day 8-13: Research how to communicate all the ideas on your lists and start adding them to your score. Bribe a musician friend with a steak dinner or something, and ask them what the symbols are for everything you don't know. By the end of day 13 your score should now say not only what notes to play, but how to play them (roughly). Sanity checks: Every part needs a dynamic level marker at the beginning of the piece, usually after long rests as well, and also should have one after every crescendo or decrescendo. If the whole piece has a dynamic level change, make sure it's marked on EVERY instrument line.
Day 14-20: Print out your parts, show them to your musician buddies, and get them to give you feedback. Your first draft is likely going to be super rough and you'll want to do this at least twice. If you can get any of the actual orchestra performers to do this, even better. By day 20 you should be able to show your parts to a musician and not have any obvious errors jumping out at them. Sanity check: this is where you have to worry about transposed parts for specific instruments. If your printed trumpet part has the same key signature as your printed violin part, you didn't do it right.
Day 21-25: Make a high-quality printed version of each part and the conductor's score. /u/Xenoceratops has some good advice here. Get someone to look over your final draft parts too. You should be burning favours left and right for feedback from multiple people at this point (or at least taking a lot of people out for food), because if you don't know a lot about scoring you might not to be able to answer questions or solve problems at the recording session.
You should have everything done by day 25, and possibly even be able to get scores to performers early (BUT BRING EXTRA COPIES TO THE SESSION). Days 26-29 are your "oh shit" buffer, for when something inevitably goes wrong.
So: hard, but not impossible. Good luck.