Welcome to the planet !!
That's not a good sign. Is your shifter really sloppy loose ???
It could be partially that but the problem is most likely in the transmission it self.
If there's noise like a bearing howl you need to get it looked at.
Know the shifter is firm...what also weird is that even when the car is off it wont hold in 1st gear...like if I pull in my driveway and put it in first it will pop out and start too roll backwards....and this only happens in first gear all others are fine
From an older thread. This will put you onto the pic of the inside of your tranny. Go to figure 2-30 under the search option Illustration Index. There's a shift rod (item 100) which controls 5th and reverse. Look at the pins associated with it. http://www.myisuzuparts.com You might also be interested in Figure 2-26 (for the 88 model; not the earlier models).
Could be as simple as a bad transmission or motor mount has shifted that assembly enough that the shifter is now touching the body, or is just being pressed by the shifter boot. Try removing the boot and see if it still pops out, or if the shifter touches the body when in 1st.
I had that happen on one of my cars....turned out it was the synchros were worn out by the prior owner (the grinding you hear whens someone isn't shifting properly). Synchros get worn out to if you rest your hand on the shifter. Bad idea.
When the synchro rings go bad you either have gears that won't shift (the teeth won't line up with the actual gear itself so the sliders can't slide onto the gear) or the gear won't stay. Synchros consist usually of three parts: two outer rings and an inner ring. The outer rings have triangular shaped teeth while the inner ring allows the "synchro" to slide and allow you to change gears. When the teeth on the slider and outer rings wear down you either cannot shift into the gear or the gear pops out under torque.
A bad fork can cause a similar issue since it allows slop in the shifting mechanism. Again by resting your hand on the shifter you can wear out the fork for the gear you are currently in.
Here's a photo I dug up to show you what could happen (not saying that it is the cause in your case, but, possible):
I had to take apart my tranny....the replacement parts cost about $10 since I found them at a local JY.