Well, define 'fix'? If it is 'sticking', you can use white-lithium bearing grease injected (in moderation) with a 12-cc syringe (sans needle) into the mechanism from the outside. If it is 'stuck' in the open-door position, this is tough but fixable. First, you must remove the bolster, pull-handle, window crank and door unlock handles. Then, remove the half-door access panel, and with great-dexterity, disconnect the linkages and then unbolt the latching assembly, replacing it with a new unit (available at the body-shop that I would drop the vehicle off at to have them do this, anyhow).
If you have a door that is in the locked-position, this is a pain, bordering on nightmare. You will do all the steps above...but as the door will be shut, you will have to get into the inside of the door and open the latch using a combination of linkage bypass (hand-manipulate the throw while using some-force to push the door open), before you can unbolt the latch. Be aware, the latches on the 1995 G20's were recalled in late 1995...and if this was not serviced during the recall, then chances were that you have the bad ones...they failed, stuck, and overall caused problems.