Well,its not that its hard,its more or less a hassle and time consuming,because you have to build amps for each line,then tweak it to your liking by changing out resistors. That is honestly what I consider to be too much a hassle. When it comes to doing all that Id rather spend a tad extra and place a new encoder in there that uses a Sony CX 1645 and run it off the RGB produced by the Genesis 1. The cost would be around the same as you'd have to pay Dean,but in the end you'd have a encoder in there with pots to adjust the RGB lines to your liking to get the picture you'd want,brighter or darker,and the encoder wouldn't be built as cheaply.
Here is a link you can take a look at.
http://www-unix.ecs.umass.edu/~dhowland/mod/As you can see,alot more effort is required,and its more time consuming. A Genesis 3 or latter model Genesis 2 Mk-1451 can be done in alot less time,with less effort,and cost alot less to do,as I stated above,I would do for $10,plus you would have to buy the parts,which would average around $5-10 bucks depending on where you got them at. All in all modding a Genesis/Megadrive 1 or older model Genesis/Megadrive 2 is more expensive either way it goes. The Sony CX 1645 in the Genesis 3 and G2 Mk-1451 is better then the older Sony CX 1145 used in Genesis 1 decks anyway. All you basically have to add each of the Sony CX 1645 lines is a 220 cap and 68-75hom resistor.