For note, the requirements that he listed above for FML is insanely more powerful in Forge/FML for MC 1.3 as it will even change classloading itself to depend on that as well, basically fixing all possible linking issues, as long as the mods use that properly.
Only Forge, NEI, CodeChickenCore, and nothing else should be in the jar, make sure everything else is in the mods directory else loading order of things can break. That includes NEI's addons, they also need to be in the mods directory.
I have not looked myself, but first I would recommend looking at the image that contains MC's fonts, see if it supports what you need, if it does not then you might need to generate one and have your signs use it instead.
In terms of MP difficulty I would probably say:
Items -> Blocks -> Items with functionality -> Entities -> Blocks with TileEntity's.
Blocks are only *barely* more difficult than Items.
Might try pressing on in to some of the harder realms soon. Making good progress!
Because when you static construct you cannot set ID's dynamically or handle failure conditions properly, nor can other mods bind to you properly or vice-versa, whole host of issues. Just do not do it.
Well we can help with Forge, but technic/tekkit modifies various things in their pack, so it is hard to help things that other people are kind of screwing with...
You need to use an MCP that is designed for 1.2.5.
You need to use the 1.2.5 minecraft.jar.
You need to use the 1.2.5 minecraft_server.jar.
You need to use a Forge for MC 1.2.5, such as 171.