Major Mike, the 1979 war and 1980s occupation of Cambodia were a long time ago. All those veterans are long retired.
The Chinese have grown immensely in terms of capability, especially air and naval as well as electronic warfare.
Vietnam has invested heavily in these capabilities but their forces are still miniscule relative to the Chinese:
6 x Kilo class subs (their main strike force.
4 Gepard class frigates (1500 ton ships so also can be categorised as corvettes)
2 x South Korean Pohang class corvettes.
48 x Su-27/-30 Flankers (at least 2 lost since)
12 x S300 SAM launcher
Overall their airforce is shrinking – there was once over 200 combat aircraft based on MiG-21Bis (superior to Chinese aircraft ala J6 and early model J7 at the time) and Su-22. Now there is 80 aircraft including 34 ageing Su-22s and 46 more modern Su-27/30s.
The Chinese operates hundreds of Flanker derivatives as well as several hundred J-10s (based on Israeli IAI Lavi) and have inducted J-20 stealth interceptors. There's also other modern aircraft ala JH-7 (similar to Tornado) and hundreds of modernised J-7s (MiG-21) and J-8 interceptors.
The Chinese also operate a large AWACS fleet whilst Vietnam have none.
The PLAN is officially a monster with 30 destroyers, 50 frigates, 40+ large corvettes and nearly 70 submarines (oh and two aircraft carriers). Most of these ships are modern with older ones being scrapped or sold off/donated.
The Vietnamese army has been largely neglected in favour of upgrading the navy and airforce. It's main tanks are still based on T55 and T62 with a mere 64 T90s acquired.
The PLA has on the other hand gone through a massive upgrade and now boasts large numbers of modern tanks as well as a large fleet of attack helicopters.
The PLA has been conducting exercises with western style forces including Turkey, Thailand and Pakistan as well as large scale exercises with Russia.
It is thus questionable how much Vietnam could do to stop the Chinese without massive assistance from else where.