Quite a bit.

The Soviet Union opened its first embassy in Hanoi in 1954. Before this time, North Vietnam had been much closer to the People's Republic of China than it had been to the Soviet Union. Beginning in the late 1950s, this started to change for a variety of reasons. By 1959, it was clearly starting to favor improved relations with the USSR.

In January 1960, Le Duan announced that North Vietnam would switch from agricultural emphasis to heavy industrial development in its first Five-Year Plan (1960-1965) and it would learn "especially from the USSR" in this approach. A Soviet scientific and technical mission arrived in spring 1960 to that end.

Following this mission, the Soviet Union granted North Vietnam substantial financial credits to buy agricultural and industrial equipment. China did as well, but owing to its internal difficulties at this time, the Soviet offer was more attractive to the North Vietnamese.

By the end of the year, Soviet advisers and supplies were flooding into Laos in the largest Soviet airlift since WWII. Between 1960 and 1962, the Soviet Union operated an airlift from Irkutsk to Hanoi and on to Vientiane with the cooperation of the Chinese government, which permitted the overflight of its territory.

With North Vietnam intensively involved in that conflict, some of the supplies were siphoned off by the Vietnamese government. As late as summer 1962, however, the CIA had not found any Soviet bloc weaponry in use by fighters in South Vietnam.

As early as 1963, according to a Chinese source, the USSR had promised North Vietnam "rocket units" (presumably surface-to-air missiles) and "one air group" of MiG-17s. Khrushchev evidently reneged on this promise, as these items did not arrive in the country until 1965. The Soviets did, however, send some heavy equipment as early as Dec. 22, 1963. A reconnaissance overflight of Haiphong in January 1964 discovered self-propelled anti-aircraft guns, which were (presumably) delivered to North Vietnam on a freighter that docked in the country on that date three days before Christmas.

Even though the Soviet Union did not begin shipping heavy equipment to North Vietnam until this point, the two countries already had extensive interactions, and the Soviet Union had been shipping lighter equipment to North Vietnam for years.

Soviet shipments of military aid remained small until about the time of the Gulf of Tonkin Incident. At that time, the North Vietnamese began urgently requesting anti-air defenses. These were slow in arriving for three main reasons: The Chinese did not allow another significant airlift, the Soviets were concerned about the vulnerability of shipping to a Cuban-style blockade, and the Chinese and Soviets had a pretty severe disagreement in 1965 over rail shipments.

Despite these obstacles, the first surface-to-air missile site began construction in March 1965 and was completed on July 24, when its Soviet crew fired its first missile. Three days later, the U.S. military bombed the site for the first time.

For more information, the CIA FOIA database has a ton of useful information. Refer to "The 1965 Sino-Soviet-Vietnamese Controversy Over Soviet Military Aid to North Vietnam" (20 Dec. 1965); "Current Intelligence Staff Study North Vietnam and Sino-Soviet Relations" (4 Mar. 1962); "The Sino-Soviet Dispute on Aid to North Vietnam (1965-1968)" (30 Sep. 1968); and "Anomalies in Soviet Shipping to North Vietnam During the First Half of 1969" (July 1969).