That simplifies things but there's still a lot to watch out for, especially at computer boundaries. You may be sending messages from Windows to a Linux server, or you may be editing files in a text editor that's configured to a different character set and feeding those into your message client.
There's excellent material on what every programmer needs to know about
Version 2 Character Sets and Encoding from Health Intersections, a paper by someone who had just finished rewriting his v2 parser.
What Every Programmer Should Know About Unicode (no excuses!)
NTE|2||0020 SPACE NTE|2||0021 ! EXCLAMATION MARK NTE|2||0022 " QUOTATION MARK NTE|2||0023 # NUMBER SIGN NTE|2||0024 $ DOLLAR SIGN NTE|2||0025 % PERCENT SIGN NTE|2||0026 & AMPERSAND NTE|2||0027 ' APOSTROPHE NTE|2||0028 ( LEFT PARENTHESIS NTE|2||0029 ) RIGHT PARENTHESIS NTE|2||002A * ASTERISK NTE|2||002B + PLUS SIGN NTE|2||002C , COMMA NTE|2||002D - HYPHEN-MINUS NTE|2||002E . FULL STOP NTE|2||002F / SOLIDUS NTE|2||0030 0 DIGIT ZERO NTE|2||0031 1 DIGIT ONE NTE|2||0032 2 DIGIT TWO NTE|2||0033 3 DIGIT THREE...and so on.
You can download a simple lab result test message here or create your own with other character sets and neat tricks like embedding escape sequences and changing encoding mid-stream (but for the sake of the rest of us who might have to read your data please don't). Then feed that into an HL7 client program, such as the free and open source HAPI Test Panel, and run it end to end through the system. If it comes out the other side the same way it went in, you're golden. Happy encoding!