What program(s) could I use on either windows or linux that would
allow me to see the garbled encrypted content for the sheer novelty of
it? Would a non-encrypted word processor document be able to be read
with all its coded formatting and text?
Use any plaintext editor like notepad.exe, Notepad++, Gedit, Leafpad, nano, vi and many more. (As the name suggests, these are editors without any fancy formatting features, instead allowing to see and modify each byte in a file).
And a MS Word doc file (as example) is not very readable, even if unencrypted. Because the formatting part is quite much, and compression algorithms (to save memory) are used.
Let's say some hacker did steal my computer and really wanted to read
the files: what would they do to try and crack the encryption? Is the
encryption key long enough in open office to make solving the
encryption key take an astronomical period of time?
You don't have a secure-randomly generated key, but just a password, right? Then it usually depends on your password: While it is used to derive a key that is usable with encryption algorithms, the attacker can derive the same key if he has the same password.
The two main possibilities for an attacker:
a) Automatically trying a long list of known passwords, because many people use something easy like 1234 (even if it is not that easy, the lists are really long...)
b) Just trying everything possible, either passwords or derived keys (usually passwords because easier). Takes often longer than a, but will find the right password for sure.
If it is feasible depends completely on your password and on the used software / file format:
Eg. old MS Office 95 has 16bit keys, independent from the password length. This is one of the cases where key guessing is easier, because there are only 65536 possible keys. Maybe this sounds much, but it's so bad that it's not even funny. Even on a modern school calculator, it wouldn't be slow enough to get a coffee.
The newest version of LibreOffice, as comparison, uses AES256+PBKDF2+SHA1: With a good password, even the best hacker shoudn't be able to do anything.
And what's a good enough password, assuming you want to protect yourself against NSA&Co.? Current realistic cracking efforts seem to be able to break 72 high entropy bit, let's use 80 to be secure. If you use a (good) password generator instead of choosing your own password, and you want passwords with uppercase+lowercase+numbers, this means you need at least 13 characters. If you choose your own password ... according to NIST (800-63), long human passwords average on 1.5 per character, this means at least 54 chacacters long.