When you force the stick into first you are putting a lot of load on the synchronisers. If you do this regularly you will shorten their life. However if you only plan to own the car 5 years or so i wouldn't worry too much.
If you double de-clutch you can get the stick smoothly into 1st at almost any speed that won't over rev the motor. Basically this is done by:
- pulling out of 2nd gear
- taking your foot off the clutch
- blipping the throttle to roughly the rpm you would be doing if you were in 1st gear at your current speed
- pushing the clutch back in
- pushing the stick into first
I do this in my 86 from time to time. Works beautifully.