sounds like 1 of 2 things
1. your synchros on 2nd and 3rd gear are starting to wear out.
2. your clutch throwout bearing is worn out

the grinding while pushing on the clutch pedal sounds like a bad or failing throwout bearing, (personal experience) ive already changed one on my car.

as far as 3rd popping out of gear, that sounds like a more serious tranny problem, either synchros or linkage or gear selector box failure
if the car doesnt like to go into second gear it could be caused by either a blown synchro (if it grinds when going in), or a bad throwout (release) bearing, the tranny can not be put into gear easily if the clutch is not disengaged via the throwout bearing.

reference:
the throwout bearing sits between the clutch pressure plate and the clutch realease fork in your tranny bell-housing
when you push on your clutch, hydraulic oil actuates a piston on the outside of your tranny (the slave cylinder), this piston pushes on a fork that enters the tranny perpendicular to the engine/tranny driveline, inside the tranny the fork pushes on a double ring with bearings inside. this allows a stationary object (the clutch release fork) to contact and actuate a spinning object (your clutch/pressure plate/flywheel bundle) to disengage your clutch. if this bearing goes bad, it will make a grinding noise in neutral when you actuate the clutch with the engine idling.

your car is factory equiped with the honda "f22a1 engine", and i believe it is the "M2L5" tranny, the same tranny as a 94 accord lx 5 speed has.

however any F series tranny or any H series tranny should fit on your engine. if you decide to get a used tranny (best value) i would look on ebay, i sold one of my trannys from another 92si i had for about $350 + shipping. that tranny was a h23a1 and would have fit your car fine, but its already sold

check out these guys:
http://www.usedengines.com/used_engines.asp

~boomer