You could try using Bullet shocks on it, but I am not completely sure they are all that different.
(My 89 had really nice ones..)
The really hard part about getting better shocks is that there really isn't an upgrade for Tomos, and most shocks are ordered by part #, so it's very hard to find shocks from another vehicle to fit to it.
Your best bet is to get a catalog from a shock absorber manufacturer that has the dimensions and specs for each one, and then find one that matches to your old ones closely.
As for the seat..if you have, or can get upholstery kits/tools, you can use that and some foam & old towels and do a fair job of it yourself, but anything past that will require some real ingenuity.
Lets us know how it goes, dude.